Showing papers on "Bicyclic molecule published in 1977"

Superiority of interconvertible enzyme cascades in metabolic regulation: analysis of monocyclic systems

Abstract: Escherichia coli glutamine synthetase and glycogen phosphorylase are prototypes for models of “closed” and “opened” bicyclic cascade systems. Steady-state functions relating the fractional activation of interconvertible enzymes to the concentrations of allosteric effectors and to the catalytic constants of the several converter enzymes in such cascades were determined. The study shows that when the active form of an interconvertible enzyme in one cycle catalyzes the covalent modification of the interconvertible enzyme in a second cycle, the two cycles become coupled, such that the fractional activity of the second interconvertible enzyme is a multiplicative function of all parameters in both cycles, i.e., of 14 and 18 parameters for the closed and the opened bicyclic cascade, respectively. Therefore, from the standpoint of cellular regulation, bicyclic cascades are superior to the monocyclic cascades analyzed previously [E. R. Stadtman & P. B. Chock (1977) Proc. Natl. Acad. Sci. USA 74, 2761-2765], because: (i) they can respond to a greater number of allosteric effectors; (ii) they can achieve much greater amplification of responses to primary stimuli (e.g., with only 2-fold changes in each parameter the amplification factors of one-cycle and two-cycle cascades are 320 and 102,400, respectively); (iii) they can generate a sigmoidal response (Hill numbers of >2) of interconvertible enzyme activity to increasing concentrations of an allosteric effector. This is because there are more steps in a bicyclic cascade at which a given effector can interact. A similar analysis of multicyclic cascade systems shows that the capacity for amplification increases exponentially as the number of cycles in the cascade increases. In addition, regulation by cyclic cascades can achieve enormous variability of the fractional activity of the interconvertible enzyme by shifting the steady-state distribution between active and inactive forms. One equivalent of ATP is consumed in each interconversion cycle to provide the energy needed to maintain the steady-state activity of the modified enzyme at a metabolically required level. Therefore, the decomposition of ATP associated with the cyclic cascade is not a wasteful process.

1,6-Anhydro Derivatives of Aldohexoses

Abstract: Publisher Summary The 1,6-anhydroaldohexopyranoses and 1,6-anhydroaldohexofuranoses are aldohexose derivatives that can be formed from free hexoses by dehydration in such a way that intramolecular glycosides containing a glycosidically linked, primary hydroxyl group are formed. Depending on whether the D-hexose adopts the pyranoid or furanoid form, two analogous, bicyclic systems are formed—namely, 1,6-anhydro-β-D-aldohexopyranoses having a 6,8-dioxabicyclo[3.2.l]octane skeleton from the former, and 1,6-anhydro- β-D-aldohexofuranose having a 2,8-dioxabicyclo[3.2. l]octane skeleton from the latter. In their chemical properties, both these types of compound resemble to a certain degree the methyl β-D-aldopyranosides or the methyl α- or β-D-aldofuranosides. They do not have reducing properties, and are relatively stable in alkaline media, but are hydrolyzed by acids to the free hexoses. A characteristic feature of these compounds is their steric rigidity in the crystalline state as well as in solution. 1,6-anhydro-β-D-hexopyranoses are widely used in the synthesis of hexoses and their derivatives, oligosaccharides, and for polymerization to polysaccharides.

Synthesis of ethylene, cyclo-octa-1,5-diene, bicyclo[2.2.1]heptene, and trans-cyclo-octene complexes of palladium(0) and platinum(0); crystal and molecular structure of tris(bicyclo[2.2.1]heptene)platinum

Abstract: Reaction of [Pt(1,5-C8H12)Cl2] with Li2(C8H8) in diethyl ether in the presence of excess of 1,5-C8H12 gives the white crystalline complex [Pt(1,5-C8H12)2] in good yield. A similar reaction of [Pd(1,5-C8H12)Cl2] in the presence of propene affords [Pd(1.5-C8H12)2]. stable below ambient temperatures. The reaction of [M(1,5-C8H12)Cl2](M = Pd or Pt) with Li2(C8H8) and excess of bicyclo[2.2.1]heptene gives, respectively, tris(bicyclo[2.2.1]heptene)- palladium and -platinum. These complexes are also obtained by displacement of cyclo-octa-1,5-diene from [M(1,5-C8H12)2](M = Pd or Pt) by bicyclo[2.2.1]heptene. Related displacement reactions with trans-cyclo-octene and ethylene afford, respectively, tris(trans-cyclo-octene)palladium, tris(trans-cyclo-octene)platinum. tris(ethylene)palladium, and tris(ethylene)platinum. The ethylene complexes are highly volatile, and can be isolated as crystalline species, although they readily deposit the metals. The structural identity of tris(bicyclo-[2.2.1]heptene)platinum has been established by analysis of single-crystal X-ray data recorded on a four-circle diffractometer both at room temperature and at 190 K. The complex is orthorhombic, space group P212121. Z= 4, a= 5.717(1), b= 10.735(4), c= 28.749(12)A, at 300 K: at 190 K a= 5.598(6), b= 10.775(16), c= 28.562(40)A. Full-matrix least-squares refinement, using 1 781 reflections, has converged to R 0.056 (R′ 0.066)(190 K data). The molecule has a trigonal-planar structure in which the maximum deviation from planarity is 0.03 A.

4-Substituted imidazo [1,2-a]quinoxalines

Abstract: A 4-substituted imidazo [1,2-a]quinoxaline of formula: ##STR1## or a pharmaceutically acceptable salt thereof wherein R1 is bonded to a ring carbon through a carbon-to-carbon linkage and is an aliphatic, cycloaliphatic, substituted phenyl, fused bicyclic aryl; or a monocyclic aryl substituted aliphatic group.

Carbene complexes. Part 11. Steric and conformational effects upon the transition-metal reactivity of electron-rich olefins and derived species; heteroatom-donor-olefin–metal (Cr0, Mo0, W0, or RhI) and 2-imidazoline-N-donor–metal complexes, and the crystal and molecular structure of tetracarbonyl[NN′N″N‴-tetramethylbi(imidazolidin-2-ylidene)-NN″]-chromium(0)

Abstract: The electron-rich olefin [:[graphic omitted]R]2, LR2, (R = Me or Et), reacts thermally with (a)[Cr(CO)6], forming [Cr(CO)5LR][(1) or (2)] or cis-[Cr(CO)4(LR2),][(3) or (4)] or(b)[Cr(η-C6H6)(CO)3], yielding [Cr(η-C6H6)(CO)2LMe], (5): [Cr(CO)5LMe], (1), forms the mixed ligand complexes cis-[Cr(AsPh3)(CO)4LMe], (6) or cis-[Cr(CO)4{C(OMe)Me}LMe], (7), upon treatment with AsPh3, or LiMe and then MeOSO2F, respectively The related olefins [:[graphic omitted]Me]2(L′Me2) and [:C(NMe2)2]2(tdae) do not afford carbene complexes with Cr0 From [M(CO)4(bhd)](M = Cr, MO, or W; bhd = bicyclo[221]hepta-2,5-dtene) each of the three olefins readily affords heteroatom-donor-olefln species [M(CO)4(olefin-NN″)] For M = MO, the latter is transformed thermally into the N′N″-carbenemolybdenum complexes, only for olefin = LMe2, but not for L′Me2 or tdae Attempted in situ syntheses of metal complexes of LH2 or LH–LEt[from HC(OMe)2NMe2, and H2NCH2CH2NH2 or H2NCH2CH2NHEt, and a MO0 or RhI reagent] lead instead to 2-imidazoline [N[graphic omitted]H2](R = H or Et)N-bonded complexes of Mo0 and RhI Carbon-13 nmr (but also ir and 1H nmr) spectra are diagnostic for differentiating the type of complex (carbene, olefln-N,N″, or imidazoline) and its stereochemistry The crystal and molecular structure of [Cr(CO)4(LMe-NN″)] shows the metal to be in an approximately octahedral environment: the mutually-trans CO ligands are bent away from the olefin fragment and have Cr–C bond lengths of 190 A compared to 182 A of those cis; the CC bond length is 134 A and there is probably little interaction with the Cr atom, the distance of closest approach being ca 30 A

A new synthesis of beta-lactams.

Abstract: The authors recently reported the regiospecific addition of heteroatomic nucleophiles to a number of Fp(olefin) cations (Fp = eta/sup 5/-C/sub 5/H/sub 5/Fe(CO)/sub 2/). Furthermore, it has been shown that oxidatively induced ligand transfer in FpR complexes (R-Fe-CO ..-->.. FeCOR) leads to carboxylation of R with retention of configuration at the migrating carbon center. It is now shown that an appropriate combination of these processes provides a facile and stereospecific synthesis of mono- and bicyclic ..beta..-lactams from olefins.

Reaction of chlorosulphonyl isocyanate with 1,3-dienes. Control of 1,2- and 1,4-addition pathways and the synthesis of aza- and oxa-bicyclic systems

Abstract: Cyclopenta-, cyclohexa-, cyclohepta- and cyclo-octa-1,3-dienes react with chlorosulphonyl isocyanate to yield, in each case, a single N-chlorosulphonyl β-lactam as the primary product. In the first three examples, these 1,2-adducts undergo stepwise thermal rearrangements with varying degrees of ease to thermodynamically more stable products of 1,4-addition (cyclisation occurring through O or N in the ambident anion) or substitution products; the β-lactam from cyclo-octadiene could not be induced to rearrange constructively. The reactivity patterns in acyclic dienes are compared and a dipolar reaction mechanism is discussed. Selected n.m.r. spectra are analysed in detail and examples of conversion of the 1,4-adducts into 2-azabicyclo[2.2.1]-heptanes, -heptenes, and -heptadienes and into 2-oxa- or 2-aza-bicyclo[2.2.2]-octanes and -octenes and -bicyclo[3.3.2]nonenes are recorded.

Anionenaktivierung, IV. Kristall‐ und Molekülstruktur des Adduktes von Malononitril mit 18‐Krone‐6 (1,4,7,10,13,16‐Hexaoxacyclooctadecan)

Abstract: Die Struktur des Adduktes 2 Malononitril · 18-Krone-6 wurde rontgenographisch bestimmt und bis zu einem R-Faktor von 0.049 verfeinert. Die Verbindung kristallisiert in der Raumgruppe P21/c. Die Malononitrilmolekule bilden uber CH · · · ·O-Wasserstoffbrucken mit dem Kronenether analog den bicyclischen Aminopolyethern einen dreidimensionalen Hohlraum von ca. 100 pm Durchmesser. Der Kronenether hat wie im KSCN-Komplex annahernd D3d-Symmetrie. Anion Activation, IV. Crystal and Molecular Structure of the Malononitrile Adduct of 18-Crown-6 (1,4,7,10,13,16-Hexaoxacyclooctadecane) The structure of the adduct 2 malononitrile · 18-crown-6 has been determined from X-ray data and refined to R = 0.049. The complex crystallizes in the space group P21/c. The molecules of malononitrile are hydrogen bonded (CH · · · ·O) to the crown ether forming a three-dimensional hole of about 100 pm diameter as observed in bicyclic amino polyethers. The complexed crown ether has approximately D3d symmetry like its KSCN complex.

Photochemische Reaktionen 94. Mitteilung. Vinyloge β‐Spaltung bei Epoxy‐enonen der Jonon‐Reihe

Abstract: Photoinduced Vinylogous β-Cleavage of Epoxy-enones of the Ionone Series The photochemistry of the α,β-unsaturated γ,δ-epoxy-enones 1–3 is determined by: (i) C(γ)-O-scission of the epoxide (vinylogous β-cleavage of Type A); (ii) C(γ)-C(δ)-cleavage of the oxirane (vinylogous β-cleavage of Type B); (iii) (E/Z)-isomerization of the enone chromophore. In contrast, 4 with tertiary C(β) shows no Type B cleavage. Type A cleavage is induced both by n,π*- and π,π*-excitation and arises probably from the T1-state, but Type B cleavage is observed only on π,π*-excitation and represents presumably a S2-reaction. On Type A cleavage 1–4 undergo 1,2-alkyl-shifts to 1,5-dicarbonyl compounds (15–18, 25–28, 34 and 35) or rearrange to dihydrofuranes (7 and 30). The isomerization 17 proceeds by a stereoselective [1,3]-sigmatropic shift. On Type B cleavage 1–3 isomerize to a bicyclic enol-ether (8, 29) or to a monocyclic enol-ether (9; product of a homosigmatropic [1,5]-shift) or undergo fragmentation to isomers such as allenes 10, 22 and 31 or cyclopropenes 11 and 21. The non-isolated, unstable (Z)-epoxy-enones 14, 19, 24 and 38 isomerize by fragmentation to the furanes 12, 23, 33 and 39 respectively, on contact with traces of acid or by heating. However, for 19 and 4, Type B cleavage may lead to the furanes 23 and 39. On UV. irradiation of the epoxy-enone 4 the initially formed (E/Z)-isomers 34 and 35 yield on π,π*-excitation the enones 37 and 40 by a vinylogous β-fragmentation. In addition, on n,π*-excitation 34 isomerizes to 35, which decarbonylates exclusively to the enone 37. The reactions of 1–4 with BF3 · O(C2H5)2 were also studied (see appendix). The epoxy-enones 1 and 2 isomerize by an 1,2-alkyl shift in good yield to the 1,4-dicarbonyl compounds 79 and 81, whereas 3 gives the 1,4-diketone 83, and in small amounts the 1,5-diketone 84. On the other hand, 4 is converted to the fluorohydroxy-enone 85 and to the 1,5-dicarbonyl product 34, the only isomer in this series which is identical with one of the photoproducts.

13C nuclear magnetic resonance studies. 64. The 13C spectra of a variety of bicyclo[3.2.1]octanols

Abstract: The 13C nmr spectra of a series of 20 bicyclo[321]octanols and -octenols have been determined to examine the shielding effects of the hydroxyl group on the skeletal carbons in this ring system For comparison, the previously unreported data for a few closely related alcohols in the [211], [221], and [322] systems were also collected The utility of these substituent effects for configuraional and conformational assignments is discussed

4-Aminosubstituted imidazo(1,2-A)quinoxalines

Abstract: A 4-substituted imidazo[1,2-a]quinoxaline of formula: ##STR1## or a pharmaceutically acceptable salt thereof wherein R 2 is hydrogen or a radical bonded to the nitrogen by a carbon to nitrogen linkage and selected from the group consisting of aliphatic, cycloaliphatic, phenyl, substituted phenyl, fused bicyclic aryl, and monocyclic aryl substituted aliphatic group.

Exo- und endo-Tricarbonyleisenkomplexe von bicyclischen 2,3-Dimethylidenverbindungen

Abstract: Exo- and endo-Tricarbonyliron Complexes of Bicyclic 2,3-Dimethylidene Compounds. The preparation of exo- and endo-tricarbonyliron complexes (exo- and endo-5, -6, -8, and 9) of 2,3-dimethylidene-5-bicyclo[2.2.1]heptene(1), -bicyclo[2.2.1]-heptane (2), -5-bicyclo[2.2.2]octene (3) and -bicyclo[2.2.2]octane (4) is described. The complexes are obtained by thermal reaction of the bicyclic butadienes with di-ironenneacarbonyl in hexane solution. exo- and endo-5 are also formed photochemically from ironpentacarbonyl and 1 in pentane solution at −35°. The structural assignment of exo- and endo-5 and -6 is based on their mass-spectra and on coordination shifts in 1H- and 13C-NMR.-spectra exo- and endo-6 are correlated with exo- and endo-5, respectively, by hydrogenation. Hydrogenation of the uncomplexed double bond in exo- and endo-5 occurs in both complexes from the exo side as shown by deuteration experiments. The free ligand 1 reacts in the same stereospecific manner.

Hydrosilylation of olefins catalysed by trans-di-µ-hydrido-bis(tricyclohexylphosphine)bis(silyl)diplatinum complexes

Abstract: The diplatinum complexes [{Pt(SiR3)(µ-H)[(C6H11)3P]}2] catalyse the addition of silanes R3SiH (R = Me, Et, PhCH2, Ph, OEt, or Cl) to pent-1-ene, hex-1-ene, styrene, allyl chloride, and 2-methylpropene. Reactivity of the silanes is qualitatively in the order: Me2EtSiH ≃ Me2PhSiH ≃ Me2(PhCH2) SiH ClMe2SiH > Me3SiH > Cl3SiH Et3SiH (EtO)3SiH, except for allyl chloride for which it is Cl3SiH > Cl2MeSiH > Me2PhSiH ClMe2SiH. The hydrosilylations are frequently strongly exothermic, proceeding in high yield with a catalyst: reactant ratio of 10–4–10–6 : 1. Hexa-1,5-diene, octa-1,7-diene, and 4-vinylcyclohexene also react readily with silanes using the same catalyst system. Hexa-1,5-diene and octa-1,7-diene afford the bis(silicon) adducts, but with 4-vinylcyclohexene only the exocyclic double bond is hydrosilylated. Catalytic addition of silanes to bicyclo[2.2.1]heptene is also described, exo-addition products being formed in 60–85% yield. The addition of Me3GeH to hex-1-ene and to styrene is catalysed by [{Pt(GeMe3)(µ-H)[(C6H11)3P]}2].

(Acylaryloxy)acetic acid diuretics. 1. (2-Alkyl- and 2,2-dialkyl-1-oxo-5-indanyloxy)acetic acids.

Abstract: The discovery of the (acryloylaryloxy)acetic acids as a new class of potent diuretics prompted the investigation of related bicyclic compounds. Annelated analogues of the parent series, the (2-alkyl- and 2,2-dialkyl-1-oxo-5-indanyloxy)acetic acids, were the subjects of this study. Those compounds, unlike the monocyclic parent compound, lacked the double bond adjacent to the carbonyl group. More importantly, they possessed both saluretic and uricosuric properties. The optimal single 2-substituents for maximal saluretic and uricosuric activity were determined. In general, better activity was observed when a second 2-alkyl substituent (especially methyl) was present in the molecule. Replacement of the carboxy substituent by 5-tetrazolyl generally resulted in a reduction in activity.

Photorearrangements of phenyloxazoles

Abstract: Various aryl oxazoles have been subjected to photolysis. The resulting photorearrangements have been classified as type A or B. Type A involves formal interchange of two adjacent ring atoms (exchange of positions 2 and 3, or 4 and 5). Type B involves formal exchange of positions 2 and 4, or 3 and 5. Irradiation of 2-phenyloxazole (18) in benzene or cyclohexane gives 3-phenyl-2H-azirine-2-carbaldehyde (19)[thermal rearrangement leads to 3-phenylisoxazole (21)] and 4-phenyloxazole (20). Similarly, irradiation of 5-methyl-2-phenyloxazole (23) results in 2-acetyl-3-phenyl-2H-azirine (24). The correlation between photolysis of the oxazole (18) and its electronic structure, as deduced from semiempirical SCF-MO and SCF-Cl calculations, is discussed. The type A rearrangement can be rationalised in terms of a ring-contraction–ring-expansion sequence. A pathway involving a bicyclic intermediate is proposed for the type B rearrangement.

Herbicidal substituted bicyclic triazoles

Abstract: Substituted bicyclic triazole compounds essentially as shown in Formula I, agricultural compositions containing them, and the method of use of these compounds as herbicides for the control of undesired vegetation in crops ##STR1##

Cationic ruthenium(II) systems. Part 1. The preparation and reactivity of diene(hydrazine)ruthenium(II) cations, and the formation of aminobonded hydrazone complexes

Abstract: The polymeric species [{RuCl2(diene)}n](1; n > 2) and the appropriate hydrazine have been used to prepare the salts [Ru(diene)(N2H4)4][BPh4]2{2; diene = bicyclo[2.2.1]hepta-2,5-diene(nbd) or cyclo-octa-1,5-diene(cod)}[Ru(cod)(NH2NHMe)4][PF6]2, and [RuH(cod)(NH2NRR′)3]X [R = R′= Me, X = BPh4(3) or X = PF6(4); R = H, R′= H or Me, X = BPh4(5)]. Solutions of (2; diene = cod) in refluxing acetone–ethanol mixtures give a complex of stoicheiometry [Ru(BPh4)(cod)](6) and, in the presence of ligands L, [Ru(cod)L4][BPh4]2[L = pyridine (py), Me2SO (dmso), or MeCN], [RuL6][BPh4]2(L = 4Me-py or dmso), and the hydrazone-containinig salts [Ru(NH2NCMe2)2L4]2{7; L = P(OMe)3, P(OEt)3, P[(OCH2)3CR](R = Me or Et), and PPh(OMe)2}. Treatment of [Ru(cod)(NH2NHMe)4][PF6]2 with PPh(OMe)2 in acetone produces [Ru(NH2NHMe)2{PPh(OMe)2}4]-[PF6]2. Substitution reactions of (3) give [RuH(cod)L3]+[L = py, 4Me-py, or MeCN] and [RuHL5]+[L = PPh(OMe)2, P(OEt)3, or PPh(OEt)2], while the neutral complexes [{RuXH(cod)}2NH2NMe2](8) have been prepared from (3) and LiX (X = Cl or Br) in methanol or acetone solutions. Complex (8) may be converted into [RuXH(PPh3)3] and [RuXH(cod)(PMePh2)2](X = Cl or Br) with PPh3 and PMePh2 respectively.

The Synthesis of Strained Methylene‐bridged Bicyclic Olefins by the Intramolecular Wittig Reaction

Abstract: A convenient synthesis of the strained methylene-bridged trans-cyclooctenes bicyclo[3.3.1]-1 (2)-nonene (1), bicyclo[4.2.1]-1(8)-nonene (2), and bicyclo[4.2.1]-1(2)-nonene (3) by the intramolecular Wittig reaction is described (see Schemes 1–4). The (3-oxocycloalkyl)alkyl-phosphonium bromides 20, 27 and 38 undergoing cyclization to the bridgehead olefins are formed by simple reaction sequences. The spectral properties (IR., 1H-NMR., 13C-NMR., and UV.) of the olefins are discussed with regard to their strain.

Calciferol and its relatives. Part 20. A synthesis of Windaus and Grundmann's C19 ketone

Abstract: Starting from 1β-[(R)-2- hydroxy-1-methylethyl]-7aβ-methyl-3aα,6,7,7aβ-tetrahydroindane (1) syntheses have been effected of two bicyclic compounds suitable as intermediates for conversion into vitamin D-active products, viz. Windaus and Grundmann's ketone (20){7aβ-methyl-1β-[(1R,4R)-1,4,5-trimethylhex-trans-2-enyl]-3aα,4,5,6,7,7aβ-hexahydroindan-4-one}, and des-AB-cholestane-8β,25-diol (23){4β-hydroxy-1β-[(R)-5-hydroxy-1,5-dimethylhexyl]-7aβ-methyl-3aα,4,5,6,7,7aβ-hexahydroindane}.

1,3-Dipolar Cycloadditions to Bicyclic Olefins. I. 1,3-Dipolar Cycloadditions to Norbornadienes

Abstract: The 1,3-dipolar cycloadditions of phenylglyoxylonitrile oxide, benzonitrile-N-phenylimine, or N-phenyl-C-p-nitrophenylnitrone to norbornadiene, 2,3-dicyanonorbornadiene, and 2,3-bis(methoxycarbonyl...

New route to bicyclic lactones: use of benzeneselenenyl chloride

Abstract: γδ-Unsaturated acids react with PhSeCl in a process that is a new general route to bicyclic lactones.

Carbon‐13 nuclear magnetic resonance spectra: V—substituent interactions at 4‐substituted adamantanones and bicyclo[2.2.2]octanones

Abstract: The 13C nmr data of a variety of 4eq- and 4ax-substituted adamantanones and bicyclo[222]octanones are presented It is shown that for a number of carbons the chemical shifts cannot be predicted by a given additivity rule The deviations of the observed chemical shifts from the calculated ones are discussed in terms of different interaction mechanisms operating through the σ bond frameworks or through space