Showing papers in "Journal of Medicinal Chemistry in 1989"

Tyrphostins I: synthesis and biological activity of protein tyrosine kinase inhibitors.

Abstract: A novel class of low molecular weight protein tyrosine kinase inhibitors is described These compounds constitute a systematic series of molecules with a progressive increase in affinity toward the substrate site of the EGF receptor kinase domain These competitive inhibitors also effectively block the EGF-dependent autophosphorylation of the receptor The potent EGF receptor kinase blockers examined were found to competitively inhibit the homologous insulin receptor kinase at 10(2)-10(3) higher inhibitor concentrations in spite of the significant homology between these protein tyrosine kinases These results demonstrate the ability to synthesize selective tyrosine kinase inhibitors The most potent EGF receptor kinase inhibitors also inhibit the EGF-dependent proliferation of A431/clone 15 cells with little or no effect on EGF independent cell growth These results demonstrate the potential use of protein tyrosine kinase inhibitors as selective antiproliferative agents for proliferative diseases caused by the hyperactivity of protein tyrosine kinases We have suggested the name "tyrphostins" for this class of antiproliferative compounds which act as protein tyrosine kinase blockers

Renin inhibitors. Synthesis of transition-state analogue inhibitors containing phosphorus acid derivatives at the scissile bond.

Abstract: The synthesis of five amino phosphorus derivatives, 1a-e, is described. The derivatives were incorporated into a series (18) of analogues of the 5-14 portion of angiotensinogen, in most cases at the scissile Leu-Val bond. The resultant compounds were tested in vitro for their ability to inhibit human plasma renin. Replacement of the scissile bond with the phosphinic analogue of Leu10-Val11 (1b) gave the most potent inhibitors, having IC50 = 7.5 x 10(-8) M for H-Pro-His-Pro-Phe-His-(1b)-Ile-His-Lys-OH and IC50 = 1.0 x 10(-7) M for Z-Arg-Arg-Pro-Phe-His-(1b)-Ile-His-NH2. The shorter phosphonic acid sequence Z-Pro-Phe-His-(1d) retained biological activity with an IC50 = 6.4 x 10(-6) M.

Modification of the hydroxy lactone ring of camptothecin: inhibition of mammalian topoisomerase I and biological activity.

Abstract: Several camptothecin derivatives containing a modified hydroxy lactone ring have been synthesized and evaluated for inhibition of topoisomerase I and cytotoxicity to mammalian cells. Each of the groups of the hydroxy lactone moiety, the carbonyl oxygen, the ring lactone oxygen, and the 20-hydroxy group, were shown to be critical for enzyme inhibition. For example the lactol, lactam, thiolactone, and 20-deoxy derivatives did not stabilize the covalent DNA-topoisomerase I complex. With a few exceptions, those compounds that did not inhibit topoisomerase I were not cytotoxic to mammalian cells. Two cytotoxic derivatives that did not inhibit topoisomerase I were shown to produce non-protein-associated DNA single-strand breaks and are likely to have a different mechanism of action. One of these compounds was tested for antitumor activity and was found to be inactive. The present findings, as well as other reports that the hydroxy lactone ring of camptothecin is critical for antitumor activity in vivo, correlate with the structure-activity relationships at the level of topoisomerase I and support the hypothesis that antitumor activity is related to inhibition of this target enzyme.

A novel lead for specific anti-HIV-1 agents: 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine.

Abstract: La synthese du compose du titre est donnee, cet analogue de nucleoside possede une activite anti-HIV-1

New hydrogen-bond potentials for use in determining energetically favorable binding sites on molecules of known structure.

Abstract: An empirical energy function designed to calculate the interaction energy of a chemical probe group, such as a carbonyl oxygen or an amine nitrogen atom, with a target molecule has been developed. This function is used to determine the sites where ligands, such as drugs, may bind to a chosen target molecule which may be a protein, a nucleic acid, a polysaccharide, or a small organic molecule. The energy function is composed of a Lennard-Jones, an electrostatic and a hydrogen-bonding term. The latter is dependent on the length and orientation of the hydrogen bond and also on the chemical nature of the hydrogen-bonding atoms. These terms have been formulated by fitting to experimental observations of hydrogen bonds in crystal structures. In the calculations, thermal motion of the hydrogen-bonding hydrogen atoms and lone-pair electrons may be taken into account. For example, in a alcoholic hydroxyl group, the hydrogen may rotate around the C-O bond at the observed tetrahedral angle. In a histidine residue, a hydrogen atom may be bonded to either of the two imidazole nitrogens and movement of this hydrogen will cause a redistribution of charge which is dependent on the nature of the probe group and the surrounding environment. The shape of some of the energy functions is demonstrated on molecules of pharmacological interest.

Potent and prolonged acting cyclic lactam analogues of alpha-melanotropin: design based on molecular dynamics.

Abstract: Utilizing results from previous structure-activity relationships and theoretical studies of alpha-melanotropin (alpha-MSH, Ac-Ser-Tyr-Ser-Met-Glu-His-Phe-Arg-Trp-Gly-Lys-Pro-Val-NH2) and its related superpotent analogues, Ac-[Nle4,D-Phe7]-alpha-MSH and Ac-[Cys4,Cys10]-alpha-MSH, we have designed a new class of alpha-MSH4-13 and alpha-MSH4-10 cyclic lactam fragment analogues of alpha-melanotropin. The cyclic peptides have the following general structures: Ac-[Nle4,Xxx5,D-Phe7,Yyy10,Gly11]-alpha-MSH4-13- NH2 and Ac-[Nle4,Xxx5,D-Phe7,Yyy10]-alpha-MSH4-10-NH2, where Xxx = Glu or Asp and Yyy = Lys, Orn, Dab, or Dpr. Formation of the lactam bridge between the side-chain groups Xxx and Yyy was performed either in solution or on a solid-phase support. Seven cyclic peptides were prepared and bioassayed for their melanotropic potency by using standard frog (Rana pipiens) and lizard (Anolis carolinensis) skin bioassays. Relative to alpha-MSH (relative potency = 1), the potencies of the cyclic peptides in the lizard skin bioassay were as follows: alpha-MSH (1); Ac-[Nle4,Glu5,D-Phe7,Lys10,Gly11]-alpha-MSH4-13- NH2 (6); Ac-[Nle4,Asp5,D-Phe7,Lys10,Gly11]-alpha-MSH4-13- NH2 (100); Ac-[Nle4,Glu5,D-Phe7,Lys10]-alpha-MSH4-10-NH2 (9); Ac-[Nle4,Asp5,D-Phe7,Lys10]-alpha-MSH4-10-NH2 (90); Ac-[Nle4,Asp5,D-Phe7,Orn10]-alpha-MSH4-10-NH2 (20); Ac-[Nle4,Asp5,D-Phe7,Dab10]-alpha-MSH4-10-NH2 (5); Ac-[Nle4,Asp5,D-Phe7,Dpr10]-alpha-MSH4-10-NH2 (5). Similar results were obtained in the frog skin bioassay, but the analogues were much less potent. Cyclic melanotropins with 23-membered rings exhibited 100-fold higher melanotropic potency than alpha-MSH with selectivity for the lizard melanocyte receptors over the frog melanocyte receptors. Increasing or decreasing the ring size of these cyclic melanotropins from 23 diminishes the biological potency of the resulting cyclic peptide. The 23- and 24-membered ring analogues showed prolonged (residual) biological activities in both biological assays, but the smaller ring systems (20, 21, 22) did not. These results provide new insights into the structural and conformational requirements of alpha-MSH and its analogues at two different types of pigment cell (melanocyte) receptors.

Synthesis of congeners and prodrugs. 3. Water-soluble prodrugs of taxol with potent antitumor activity

Abstract: Taxol has shown good in vivo antitumor activity in a number of test systems. The formulation of taxol for antitumor testing has been difficult. Esterification at either C-2' or C-7 resulted in loss of in vitro tubulin assembly activity but not cytotoxicity. These observations suggested that esters at C-2' and/or C-7, which would tend to promote water solubility, might serve as useful prodrugs of taxol. The reaction of taxol with either succinic anhydride or glutaric anhydride in pyridine solution at room temperature gave the crystalline mono 2'-adducts 1b and 1f, respectively. Salts of these acids (1b, 1f, 1i) were formed by the addition of 1 equiv of the corresponding base, followed by evaporation and/or freeze-drying of the solvent(s). The salts had improved antitumor activity as compared to the free acids. The triethanolamine and N-methylglucamine salts showed greatly improved aqueous solubility and were more active than the sodium salts. The glutarate series was preferred because of the higher activity and the higher yields obtained. 2'-Glutaryltaxol (1f) was coupled with 3-(dimethylamino)-1-propylamine, using CDI, to form in excellent yield the amino amide 1o. The hydrochloride salt (1p) showed good solubility and was extremely potent and active. At 10 mg/kg, in the B16 screen, 1p gave a T/C of 352 with 5 out of 10 cures. In the MX-1 breast xenograft assay, this prodrug gave values of -100 at doses of 40 and 20 mg/kg, with all live animals being tumor free.

Chemical and biological properties of a new series of cis-diammineplatinum(II) antitumor agents containing three nitrogen donors: cis-[Pt(NH3)2(N-donor)Cl]+.

Abstract: A series of 32 cationic platinum(II) complexes of the form cis-[PtA2(Am)Cl]+, where A is a monodentate (NH3 or i-PrNH2) or A2 is a bidentate (ethylenediamine or 1,2-diaminocyclohexane) amine and Am is either a heterocyclic amine based on a pyridine, pyrimidine, purine, piperidine, or a saturated amine (RNH2) ligand, was prepared and screened against in vivo murine tumor models. Each compound was tested against Sarcoma 180 ascites (S180a) in mice, with 20 members of the series showing activity (ILS greater than 50%). Antitumor activity also was demonstrated in 4 of 16 compounds tested in the L1210 murine leukemia model (ILS greater than 25%) and in 3 of 3 tested in the P388 murine leukemia model (ILS greater than 30%). The most active and potent analogues of the series were obtained when A was NH3 and Am was N1-pyridine, N1-4-methylpyridine, N1-4-bromopyridine, N1-4-chloropyridine, N3-cytosine, or N7-2'-deoxyguanosine. Complexes containing chelating and saturated amine ligands (A), as well as two trans isomers of active cis analogues (trans-[Pt(NH3)2(Am)Cl]+, where Am = N1-pyridine or N1-4-methylpyridine), were inactive in the S180a screen. All complexes were characterized by means of elemental analysis, HPLC, and 195Pt NMR spectroscopy, and the structure of one analogue, cis-[Pt(NH3)2(N3-cytosine)Cl](NO3), was determined by using single-crystal X-ray diffraction methods. While members of this series of compounds demonstrate antitumor activity in vivo, these new agents are not classical analogues of cisplatin (i.e. cis-[PtA2X2] complexes), as they contain three nitrogen donors and only one leaving group. The results of these studies suggest that further work should be conducted to better define the limits of the structure-activity relationships among platinum(II) complexes.

Synthesis, in vitro acetylcholine-storage-blocking activities, and biological properties of derivatives and analogues of trans-2-(4-phenylpiperidino)cyclohexanol (vesamicol).

Abstract: Eighty-four analogues and derivatives of the acetylcholine-storage-blocking drug trans-2-(4-phenylpiperidino)-cyclohexanol (vesamicol) were synthesized, and their potencies were evaluated with the acetylcholine active-transport assay utilizing purified synaptic vesicles from Torpedo electric organ. The parent drug exhibits enantioselectivity, with (-)-vesamicol being 25-fold more potent than (+)-vesamicol. The atomic structure and absolute configuration of (+)-vesamicol were determined by X-ray crystallography. The absolute configuration of (-)-vesamicol is 1R,2R. Structure-activity evidence indicates that (-)-vesamicol does not act as an acetylcholine analogue. Alterations to all three rings can have large effects on potency. Unexpectedly, analogues locking the alcohol and ammonium groups trans-diequatorial or trans-diaxial both exhibit good potency. A potent benzovesamicol family has been discovered that is suitable for facile elaboration of the sort useful in affinity labeling and affinity chromatography applications. A good correlation was found between potencies as assessed by the acetylcholine transport assay and LD50 values in mouse.

Antibacterials. Synthesis and structure-activity studies of 3-aryl-2-oxooxazolidines. 2. The "A" group.

Abstract: The synthesis and structure-activity relationship (SAR) studies of the effect of varying the "A" group in a series of 5-(acetamidomethyl)oxazolidonone antibacterials (2) are described. Compounds 2 were principally prepared either by the six-step synthesis described previously (J. Med. Chem. 1989, 32, 1673) or by elaboration of the synthetic intermediate 2 (A = H) via electrophilic aromatic substitution or elaboration of the intermediate 2 (A = I) by transition metal catalyzed carbon-carbon bond-forming reactions. Antibacterial evaluation of compounds 2 with A = alkyl, ethenyl, ethynyl, hydroxyalkyl, aldo and keto, oximinoakyl, carboalkoxy, nitro, amino, halo and psi-halo, alkylthio, alkylsulfinyl, and alkysulfonyl against Staphylococcus aureus and Enterococcus faecalis led to the identification of several SAR trends. In several series of homologues (alkyl, ketyl, aximinoalkyl, amino, halo and psi-halo, and alkythio), antibacterial activity increased with increasing lipophilicity. But in series with where A is a substituent with a trior tetrasubstituted (substituent larger than H) quaternary atom attached directly to the aromatic ring (hydroxyalkyl, alkylsulfinyl, alkylsufonyl), the activity peaked at the member of the series with the "tert-butyl" connectivity pattern. Conjugated electron-withdrawing substituents also had increased activity relative to nonconjugated analogues of comparable lipophilicity.

1-(2,3-Dideoxy-beta-D-glycero-pent-2-enofuranosyl)thymine. A highly potent and selective anti-HIV agent.

Abstract: The nucleoside analogue 1-(2,3-dideoxy-beta-D-glycero-pent-2-enofuranosyl)thymine (d4T, 1) was prepared by ring opening of the 3',5'-anhydro compound 5. This method has been refined such that it can be used to prepare d4T on a large scale. The triphosphate of d4T was also synthesized from 1 in order to examine the mode of action. The in vitro inhibitory activity of d4T was found to be comparable to that of AZT in HIV-infected CEM cells. The triphosphate of d4T (8) and that of AZT inhibited the HIV reverse transcriptase with poly(rA):oligo(dT) as the template:primer with Ki values of 0.032 and 0.007 microM, respectively. The in vitro toxicity of d4T against normal human hematopoietic progenitor cells (CFU-GM) was measured in comparison to AZT. While d4T reduces colony-forming units by 50% at a concentration of 100 microM, it takes only 1 microM AZT to have a similar toxic effect. With erythrocyte burst forming units (BFU-E) the in vitro toxicities for d4T and AZT have comparable ID50 values of 10 and 6.7 microM, respectively.

Studies on hindered phenols and analogues. 1. Hypolipidemic and hypoglycemic agents with ability to inhibit lipid peroxidation.

Abstract: A series of hindered phenols were investigated as hypolipidemic and/or hypoglycemic agents with ability to inhibit lipid peroxidation. 1,3-Benzoxathioles (9 and 22), phenoxypentanoic acid (34), phenoxypentanol (35a), phenoxynonanol (35b), phenylchloropropionic acid having a chromanyl group (25), and a thiazolidine compound (27) derived from 25, all having a hindered phenol group, were prepared and examined. Compound 27 showed the expected biological properties in vivo and in vitro without any liver weight increase. Biological activities of the analogous thiazolidine compounds, 43-58, were compared. Thus, (+/-)-5-[4-[(6-hydroxy-2,5,7,8-tetramethylchroman-2-yl)methoxy]- benzyl]-2,4-thiazolidinedione (27) (CS-045) was found to have all of our expected properties and was selected as a candidate for further development as a hypoglycemic and hypolipidemic agent.

2,4-Diamino-5-benzylpyrimidines and analogs as antibacterial agents. 12. 1,2-Dihydroquinolylmethyl analogs with high activity and specificity for bacterial dihydrofolate reductase

Abstract: Twelve 2,4-diamino-5-[(1,2-dihydro-6-quinolyl)methyl]pyrimidines containing gem-dimethyl or fluoromethyl substituents at the 2-position of the dihydroquinoline ring were prepared by condensations of dihydroquinolines with 2,4-diamino-5-(hydroxymethyl)pyrimidine. The dihydroquinolines were produced from the reaction of anilines with mesityl oxide or fluoroacetone. In some cases, 1-aryl-2,4-dimethylpyrroles were obtained as byproducts. Most of these pyrimidines were highly inhibitory to Escherichia coli dihydrofolate reductase (DHFR) and also had high specificity for the bacterial enzyme. 2,4-Diamino-5-[[1,2-dihydro-2,4-dimethyl-3-fluoro-2-(fluoromethyl)-8- methoxy-6(1H)quinolyl]methyl]pyrimidine had an apparent Ki value for E. coli DHFR 13 times lower than that of the control, trimethoprim (1), and was 1 order of magnitude more selective for the bacterial enzyme. It had outstanding activity against Gram-positive organisms in vitro, as well as broad-spectrum antibacterial activity equivalent to that of 1. The results of in vivo testing will be reported elsewhere. The gem-dimethyl substituents of the dihydroquinoline derivatives are considered to be responsible for the high selectivity, as well as contributing to potent bacterial DHFR inhibition. Molecular models are presented which suggest the probable interactions with the bacterial enzyme.

Thienothiopyran-2-sulfonamides: novel topically active carbonic anhydrase inhibitors for the treatment of glaucoma.

Abstract: The bulk of aqueous humor entering the eye is produced through an active secretory process by the nonpigmented epithelial cells of the ciliary process. Carbonic anhydrase is present in these cells, and following inhibition of the enzyme, bicarbonate formation is decreased, which, in turn, diminishes sodium and fluid secretion into the eye. The biological profile of the thienothiopyrans was assessed through in vitro, ex vivo, and in vivo studies. In vitro determination of I 50 and K i values utilized HCA-II, the isozyme found in the human ciliary process

Dermorphin analogues carrying an increased positive net charge in their "message" domain display extremely high mu opioid receptor selectivity.

Abstract: According to the membrane compartment concept the receptor specificity of ligands is based not only on ligand-receptor complementarity but also on specific ligand-membrane interactions. Elaboration of this concept for opioid peptide-receptor interactions had led to the assumption that mu- and delta-receptors are located in anionic and cationic membrane compartments, respectively, and to the prediction that positively charged opioid receptor ligands should display mu-receptor selectivity. To assess the validity of this model, we synthesized a series of dermorphin analogues carrying a net positive charge and tested them in mu- and delta-receptor representative binding assays and bioassays. Some but not all of the prepared compounds showed the receptor-selectivity profile expected on the basis of the membrane compartment concept. In particular, gradual augmentation of the positive charge from 1+ to 3+ in a series of dermorphin-(1-4) tetrapeptide analogues produced an enhancement of mu-receptor affinity and a progressive decrease in delta-receptor affinity, resulting in increasingly higher mu-receptor selectivity. The most selective compound was [D-Arg2,Lys4]dermorphin-(1-4)-amide (DALDA), showing a selectivity ratio (Ki delta/Ki mu = 11,400) more than 10 times higher than that of DAGO (Ki delta /Ki mu = 1050) and, thus, displaying unprecedented mu-receptor specificity. Because of its high positive charge (3+), DALDA may be particularly useful as a very specific agonist for studying peripheral mu-receptor interactions.

Dihydropyrimidines: novel calcium antagonists with potent and long-lasting vasodilative and antihypertensive activity.

Abstract: The novel calcium antagonists 3-N-substituted-3,4-dihydropyrimidines 1 and 9 and 3-N-substituted-dihydro-pyrimidin-2(1H)-ones 8 were regioselectively synthesized in good yields. Compounds 1 [especially 1s [R1 = (CH2)2N(benzyl)(2-naphthylmethyl), R2 = i-Pr, X = 0-NO2] and 1t [R1 = (CH2)2N(benzyl)(3,4-dichlorobenzyl), R2 = i-Pr, X = 0-NO2]] exhibited not only more potent and longer lasting vasodilative action but also a hypotensive activity with slow onset as compared with dihydropyridines. Moreover, some dihydropyrimidines [1q [R1 = (CH2)2N(benzyl)(3-phenylpropyl), R2 = CH2(cyclopropyl), X = 0-NO2], 1s, and 1t] were weaker in blocking atrioventricular conduction in anesthetized open-chest dogs and less toxic than the dihydropyridines.

Synthesis of some novel potent and selective catechol O-methyltransferase inhibitors.

Abstract: A series of disubstituted catechol derivatives was synthesized and tested as potential COMT inhibitors. The most active compounds were more than 1000 times more potent (IC50 = 3-6 nM) in vitro than the known COMT inhibitor, 3',4'-dihydroxy-2-methylpropiophenone (U 0521, IC50 = 6000 nM). The new compounds were also highly selective COMT inhibitors with no activity against other essential enzymes involved in the synthesis and metabolism of catecholamines.

Potential antitumor agents. 57. 2-Phenylquinoline-8-carboxamides as "minimal" DNA-intercalating antitumor agents with in vivo solid tumor activity.

Abstract: A series of phenyl-substituted derivatives of the "minimal" DNA-intercalating agent N-[2-(dimethylamino)-ethyl]-2-phenylquinoline-8-carboxamide (1) have been synthesized and evaluated for in vivo antitumor activity, in a continuing search for active compounds of this class with the lowest possible DNA association constants. Substitution on the 2'-position of the phenyl ring gave compounds of lower DNA binding ability that did not intercalate DNA, indicating that it is necessary for the phenyl ring to be essentially coplanar with the quinoline for intercalative binding. An extensive series of 4'-substituted derivatives was evaluated, but there was no overall relationship between biological activity and substituent lipophilic or electronic properties. However, several compounds showed good solid tumor activity, with the 4'-aza derivative 18 being clearly superior to the parent compound, effecting about 50% cures in both leukemia and solid tumor models.

Novel cytotoxic compounds from the ascidian Lissoclinum bistratum.

Abstract: The isolation and structures of two new cyclic hexapeptides and two new macrocyclic ethers from the aplousobranch ascidian Lissoclinum bistratum are described. Their structures were determined by two-dimensional NMR techniques. The hexapeptides, named bistratamide A and bistratamide B, differ only by the presence or absence of one double bond. They were tested for cytotoxicity toward human fibroblast and tumor cell lines and displayed similar toxicities to the octapeptides called patellamides from Lissoclinum patella. The peptides are found within the obligate algal symbiont Prochloron but clearly differ from peptides isolated from the same Prochloron of L. patella. The macrocyclic ethers isolated from L. bistratum are exceedingly potent in cytotoxicity. They have been named bistratenes A and B, and structures for these compounds are proposed.

Synthesis and antiviral activity of the nucleotide analogue (S)-1-[3-hydroxy-2-(phosphonylmethoxy)propyl]cytosine.

Abstract: The acyclic nucleotide analogue (S)-1-[3-hydroxy-2-(phosphonylmethoxy)propyl] cytosine (2, HPMPC) was prepared on a multigram scale in 18% overall yield starting from (R)-2,3-O-isopropylideneglycerol. The key step in the nine-step synthetic route is coupling of cytosine with the side-chain derivative 8 which bears a protected phosphonylmethyl ether group. In vitro data showed that HPMPC has good activity against herpes simplex virus types 1 and 2, although it was 10-fold less potent than acyclovir [AVC, 9-[(2-hydroxyethoxy)methyl]guanine]. By comparison, HPMPC exhibited greater activity than ACV against a thymidine kinase deficient strain of HSV 1 and was more potent than ganciclovir [DHPG, 9-[(1,3-dihydroxy-2-propoxy)methyl]guanine] against human cytomegalovirus. In vivo, HPMPC showed exceptional potency against HSV 1 systemic infection in mice, having an ED50 of 0.1 mg/kg per day (ip) compared with 50 mg/kg per day for ACV. HPMPC was also more efficacious than ACV in the topical treatment of HSV 1 induced cutaneous lesions in guinea pigs.

Structure-activity relationships of pyrimidine nucleosides as antiviral agents for human immunodeficiency virus type 1 in peripheral blood mononuclear cells.

Abstract: The structure-activity relationships of several pyrimidine nucleosides related to 3'-azido-3'-deoxythymidine (AZT) were determined in human immunodeficiency virus type 1 (HIV-1) infected human peripheral blood mononuclear cells These studies indicated that nucleosides with a 3'-azido group on the sugar ring exhibited the most potent antiviral activity Substitution at C-5 with H, CH3, and C2H5 produced derivatives with the highest potency, whereas alkyl functions greater than C2, including bromovinyl substitution reduced the antiviral potency significantly Changing the 3'-azido function to an amino or iodo group reduced the antiviral activity Replacement of the uracil ring by cytosine or 5-methylcytosine produced analogues with high potency and low toxicity Modification of the 5'-hydroxy group markedly reduced the antiviral activity Similarly, various C-nucleoside analogues related to AZT and 2',3'-dideoxycytidine were inactive and nontoxic From these systematic studies 3'-azido-2',3'-dideoxyuridine (5a), 3'-azido-5-ethyl-2',3'-dideoxyuridine (5c), and 3'-azido-2',3'-dideoxycytidine (7a) and its 5-methyl analogue (7b) were identified as potent and selective anti-HIV-1 agent in primary human lymphocytes

New cyclic peptides with cytotoxic activity from the ascidian Lissoclinum patella.

Abstract: The isolation and structures of a new patellamide (patellamide D) and two new lissoclinamides (lissoclinamides 4 and 5) from the aplousobranch ascidian Lissoclinum patella are described. Structures were determined largely by using two-dimensional NMR techniques and mass spectrometry. These peptides and other members of the patellamide and lissoclinamide families that have been reported previously are found withii the obligate algal symbiont of the genus Prochloron. The cytotoxicities of the compounds toward fibroblast and tumor cell lines are reported. One of these comwunds. lissoclinamide 4. is markedlv more toxic than other members of the family. Structureactivity relationships are' discussed.

New antitumor monoclonal antibody-vinca conjugates LY203725 and related compounds: design, preparation, and representative in vivo activity.

Abstract: A method has been developed to allow the direct coupling of the cytotoxic vinca alkaloid 4-desacetylvinblastine-3-carbohydrazide (DAVLB hydrazide) to a variety of murine monoclonal antibodies directed against human solid tumors. Periodate oxidation of carbohydrate residues on the antibodies, followed by reaction with DAVLB hydrazide in aqueous acid affords, in most cases, conjugates with conjugation ratios of 4-6 vincas per antibody in high yield without significantly impairing antigen binding or solubility. The outcome of the conjugation reaction is highly dependent on the concentration of, and time of exposure of the protein to, the oxidant. These conjugates exhibit potent antitumor activity in vivo against a number of human solid tumor-nude mouse xenografts, with efficacy and safety increased over unconjugated DAVLB hydrazide. This antitumor activity is also superior to that of similarly prepared but nontarget tumor binding antibody-DAVLB hydrazide conjugates. MoAb-DAVLB hydrazide conjugates release DAVLB hydrazide in solution in a temperature- and pH-dependent manner. Hydrolytic release of unmodified DAVLB hydrazide from tumor-localized MoAb-DAVLB hydrazide conjugates in vivo may be an important factor in their antitumor activity.

Synthesis, DNA-binding properties, and antitumor activity of novel distamycin derivatives.

Abstract: A group of potential alkylating agents have been synthesized that are structurally related to the oligopeptide antiviral antibiotic distamycin. All derivatives form complexes with native calf-thymus DNA but compounds 2, 3, and 6 give rise to covalent adducts. Cytostatic activity against both human and murine tumor cell lines in vitro is displayed by the new compounds. Compounds 3 and 4 are active on melphalan-resistant L1210 leukemia in mice.

Novel benzodiazepine receptor partial agonists: oxadiazolylimidazobenzodiazepines.

Abstract: The synthesis and biochemical evaluation of a series of oxadiazole derivatives of imidazobenzodiazepines related to the benzodiazepine antagonist Ro 15-1788 (2a) are reported. Although the oxadiazole ring is seen as an isosteric replacement for the ester linkage, significant differences in structure-activity trends were observed. Specifically, oxadiazoles 9-12 invariably had increased receptor efficacy (as witnessed by measurements of the GABA shift) relative to the corresponding ester. Additionally, and in direct contrast to the classical agonists such as diazepam, affinity for the benzodiazepine receptor was enhanced by a 7- rather than 8-halo substituent. The results are discussed in terms of a six-point receptor-binding model originally based on the X-ray structure of 2a. For comparison, the crystal structures of two representative oxadiazole derivatives, 10h and 12o, having a 6-oxo and 6-phenyl group, respectively, were determined and the data incorporated into a modified binding model to account for the greater efficacy of these compounds. It is concluded that the antagonist behavior of 2a relies upon the hydrogen-bond-acceptor properties of the ester carbonyl oxygen whereas for the oxadiazole series this site is localized at the imidazole nitrogen.

Design of potential anti-HIV agents. 1. Mannosidase inhibitors

Abstract: A molecular orbital and molecular graphics study of 12 substrates, inhibitors, reaction intermediates, and substrate analogues of alpha-mannosidase was undertaken. The results indicated that potent inhibitors must be good topographical analogues of the mannopyranosyl cation, an intermediate in the reaction catalyzed by the enzyme. Enzyme recognition and strong binding by the inhibitors requires that they contain, as part of their structure, electronegative atoms which are the topographical equivalent of the mannosyl cation C2 and C3 hydroxyl groups and ring heteroatom. The absence of a topographical analogue of the C4 hydroxyl group of the cation appeared to have little effect on the binding and activity of inhibitors. These results have been utilized in the design of potential anti-HIV drugs whose synthesis is now under consideration.

Synthesis and in vitro pharmacology of arpromidine and related phenyl(pyridylalkyl)guanidines, a potential new class of positive inotropic drugs.

Abstract: Replacement of the cimetidine moiety in impromidine (1,N1-[3-(1H-imidazol-4-yl)propyl]-N2-[2-[[(5-methyl-1H-imidazol-4- yl)methyl]thio]ethyl]guanidine) by more lipophilic H2-nonspecific pheniramine-like structures resulted in potent H2 agonists with up to 160 times the activity of histamine in the isolated, spontaneously beating guinea pig right atrium. Additionally, the compounds proved to be moderate H1 antagonists. Highest H2-agonistic potency was found in compounds characterized by a three-membered carbon chain connecting the aromatic rings and the guanidine group. The activity in the atrium was increased 2-4-fold by halogen substituents in the meta or para position of the phenyl ring. Highest H1-antagonistic potency resides in the group of para-halogenated compounds, p-F representing the optimal substituent in both receptor models. The corresponding guanidine 52 (arpromidine, N1-[3-(4-fluorophenyl)-3-pyridin-2-ylpropyl]-N2-[3-(1H-imidazol-4- yl)propyl]guanidine) combines about 100 times the activity of histamine at the H2 receptor with H1-antagonistic potency in the range of pheniramine. Further increase in the activity on the atrium was achieved by disubstitution with halogen on the phenyl ring, such as 3,4-F2, 3,5-F2, and 3,4-Cl2 (63-65). The 2-pyridyl group in arpromidine was replaced by 3-pyridyl without significant change in H2 agonistic activity, whereas the 4-pyridyl and phenyl analogues were less active. The rank order of potency in the atrium was in good agreement with the positive inotropic effects found in isolated, perfused guinea pig hearts, where 63-65 were the most potent compounds as well.