Showing papers on "Oxazolidine published in 2008"

Highly Diastereoselective Synthetic Route to Enantiopure β2-Amino Acids and γ-Amino Alcohols Using a Fluorinated Oxazolidine (Fox) as Chiral Auxiliary

Abstract: The alkylation reactions of an amide enolate derived from a trifluoromethylated oxazolidine (Fox) chiral auxiliary occur with a complete diastereoselectivity and in good yields with various electrophiles. This reaction provides a versatile and straightforward strategy for the synthesis of β2-amino acids and γ-amino alcohols in enantiopure form.

Highly enantioselective alkynylation of aldehydes catalyzed by a new oxazolidine–titanium complex

Abstract: The readily available and inexpensive new chiral oxazolidine in combination with Ti(O(i)Pr)(4) was found to catalyze the reaction of an alkynylzinc reagent with various types of aldehydes to generate chiral propargylic alcohols with high enantioselectivities (up to 95%) and excellent yields (up to 98%).

Axially chiral N-(o-aryl)-2-thioxo-oxazolidine-4-one and rhodanine derivatives: enantiomeric separation and determination of racemization barriers

Abstract: Axially chiral 5,5-dimethyl-3-( o -aryl)rhodanine, 3-( o -aryl)rhodanine and 5,5-dimethyl-3-( o -aryl)-2-thioxo-4-oxazolidinone derivatives have been synthesized as racemates and the energy barriers to enantiomerization have been determined by dynamic 1 H NMR or by following the thermal equilibration of the separated enantiomers using chiral HPLC. The barriers to rotation about the N sp2 –C aryl single bond were found to be 82–129 kJ/mol. The racemization barriers in these compounds are affected by the size of the ortho -substituent on the aryl ring. The magnitude of the barriers was found to change linearly with the van der Waals radii of the ortho -halogen substituents.

Chiral, hemilabile palladium(II) complexes of tridentate oxazolidines, including C2-symmetric "pincers".

Abstract: Two classes of diastereomerically enriched chiral tridentate ligands incorporating either two oxazolidine and one pyridine ( 1) or two pyridine and one oxazolidine ( 2a-c) donor groups have been made in a high-yielding modular fashion from readily available enantiopure amino alcohols and aldehydes. Both ligand classes readily formed metal complexes via 1:1 reactions with trans-PdCl 2(PhCN) 2. The compounds Pd( 1)Cl 2 and Pd( 2a-c)Cl 2 were formed as mixtures of 3 and 2 diastereomers, respectively, owing to indeterminate absolute configuration at the C (2) position of their constituent oxazolidine rings. Within each diastereomeric manifold, the metal complexes existed as equilibrium mixtures of bi- and tridentate isomers in solution, the interconversion between which was very rapid even at -50 degrees C. The fluxional nature of the compounds was inferred from a combination of (1)H and (15)N NMR spectroscopic and solution conductivity data. Substitution of one chloride ligand for hexafluorophosphate gave as mixtures of diastereomers the salts [Pd( 1-kappa N,kappa (2) N')Cl]PF 6 ( 8) and [Pd( 2a-c-kappa N,kappa N',kappa N'')Cl]PF 6 ( 12a-c) in which the ligands were coordinated through all three N-donors. A single recrystallization of 8 gave in optically pure form the major diastereomer 8 ( maj ), which was characterized crystallographically. Complexes of 2a-c differed substantially from those of the bis(pyridylmethyl)amine (bpma) ligand family with which they shared direct atom-for-atom connectivity in the coordinating groups. The amines are known to form exclusively the static tridentate complexes [PdCl(bpma-kappa N,kappa (2) N')]Cl; the difference was attributed to torsional strain associated with the rigid oxazolidine ring in tricoordinated 2a-c.

New fast and practical method for the enantioselective synthesis of α-vinyl, α-alkyl quaternary α-amino acids

Abstract: We describe a fast and practical enantioselective synthesis of ( S )- N -Cbz-α-vinyl, phenylalanine, suitable for the preparation of different N -Cbz-α-vinyl aminoacids of both configurations. The new protocol exploits a Wittig reaction on highly enantiomeric enriched N -Cbz-α-formyl-α-alkyl amino esters, readily accessible from ( l )-serine through a stereoselective alkylation of Seebach’s oxazolidine, carried out with a significant improvement of the previously reported method. The synthetic scheme is suitable for gram scale preparation of the desired product with a 94% ee.

Enantioselective synthesis of (S)-1,6,7,8,9,9a-hexahydroquinolizin-4-one. Formal synthesis of the lycopodium alkaloids senepodine G and cermizine C

Abstract: The synthesis of the title compound, a key intermediate in the synthesis of some lycopodium and lupin alkaloids, is reported. From a stereochemical standpoint the key steps are the stereoselective cyclocondensation of ketodiester 1 with (R)-phenylglycinol and the stereocontrolled reduction, with retention of configuration, of the oxazolidine ring in the resulting oxazolopiperidone lactam 2.

Insecticidal and neuroblocking potencies of variants of the thiazolidine moiety of thiacloprid and quantitative relationship study for the key neonicotinoid pharmacophore

Abstract: The pharmacophore of the neonicotinoid insecticide thiacloprid, cyanoiminothiazolidine, was modified to heterocycles such as imidazolidine, pyrrolidine and oxazolidine (the central ring hereafter). Their 6-chloro-3-pyridylmethyl or 5-chloro-3-thiazolylmethyl derivatives were examined for insecticidal activity against the American cockroach by injection and neuroblocking activity using the cockroach ganglion. The derivatives showed strong insecticidal activity with the minimum lethal dose (MLD) of about 10 nmol, which were however mostly weaker than the corresponding nitromethylene or nitroimine compounds. The activity was enhanced in the presence of synergists. The neuroblocking effect of cyanoimino compounds was at the micromolar level. Quantitative analysis for 23 variants of the key pharmacophore, constructed with the central ring conjugated to an NCN, CHNO 2 , or NNO 2 , showed that the neuroblocking potency is proportional to the Mulliken charge on the nitro oxygen atom or cyano nitrogen atom. The optimum log P value was evaluated as 1.19. The equation for the insecticidal- vs. the neuroblocking-potencies indicated that both potencies are related proportionally with each other when the other factors are the same.

An investigation about the effect of oxazolidine on modified valonia extract tanning

Abstract: This study is aimed at combining the usage of valonia and modified valonia extracts with oxazolidine to obtain an increase in hydrothermal stability, and thus to develop tanning efficiency and to produce leathers that have better properties then the ones tanned with valonia extract only. Natural and three modified valonia extracts and oxazolidine were used as tanning materials. Skin samples were divided into two groups. In group A, valonia extracts were used as tanning materials and oxazolidine as retanning agent. Group A was divided into 4 subgroups according to the used extract type. Each subgroup was also separated into four lots according to the oxazolidine percentages used. Group B where oxazolidine was used as pretanning while valonia extracts as tanning agents, was divided into three subgroups according of oxazolidine usage. Each subgroup had four lots according to the used extracts. General means of Shrinkage Temperatures (Ts) for natural extract, group A and B were found as 65.66, 78.62 and 83.42 o C, respectively, indicating that the oxazolidine pretanning followed by valonia retanning provides better tanning efficiency. On the base of the unique experiment, 4% oxazolidine and 20% least modified vegetable tannin combination gave the best result.

Method for production of sugar oxazoline derivative

Abstract: Disclosed is a method for producing an oxazoline derivative from a non-protected sugar in a simple manner. Also disclosed is a method for producing a glycoside by utilizing the product of the aforementioned method. A sugar oxazoline derivative is synthesized in one step in an aqueous solution from a sugar having a free hemiacetal hydroxy group and an amide group by using a haloformamidinium derivative as a dehydration/condensation agent. A glycoside is produced by using the oxazolidine derivative as a sugar donor and also using a sugar dehydrogenase. The method can be applied to the production of a compound having a long sugar chain, and is therefore useful for the production of a physiologically active oligosaccharide, a carrier for a drug delivery system, a surfactant, a carbohydrate pharmaceutical, a glycopeptide, a glycoprotein, a carbohydrate polymer or the like.

Convenient One-Pot Synthesis of Chiral Tetrahydropyridines via a Multicomponent Reaction

Abstract: The multicomponent condensation of various β-dicarbonyl compounds, acrolein and ( S)-2-phenylglycinol was found to provide a one-pot access to chiral 6-carbonyl-3-phenyl-2,3,8,8a-tetrahydro-7 H-[1,3]oxazolo[3,2- A]pyridines. The value of this methodology is illustrated by the short and efficient synthesis of (-)-lupinine.

Reactions of diazoalkanes with unsaturated compounds 16. Catalytic reactions of diazomethane with 2-alkenyl-1,3-oxazolidines and 2-alkenyl-1,3-oxathiolanes

Abstract: The influence of 1,3-oxazolidine and 1,3-oxathiolane fragments in substituted alkenes on the direction of their catalytic reaction with diazomethane has been investigated. The olefins bearing an oxazolidine substituent in the α- or γ-position and an oxathiolane substituent in the γ-position relative to the C=C bond react with diazomethane in the presence of Pd(acac)2 selectively resulting in cyclopropanation products. The use of Cu(OTf)2 does not result in cyclopropanation; however Cu(OTf)2 catalyzes the reaction of diazomethane with 2-(alk-1-enyl)-1,3-oxathiolanes yielding 2,3,5,6-tetrahydro-1,4-oxathiocines formed through the [2,3]-sigmatropic rearrangement of the intermediate sulfonium ylides.

Crystal Structure of Linezolid

Abstract: The crystal of the title compound, C16H20FN3O4, belongs to space group P1 with cell dimensions of a = 6.5885(9), b = 10.977(1), c = 12.919(1)A, α = 69.315(9), β = 88.17(1), and γ = 74.23(1)°. The final R value is 0.050. The key structural feature of the molecule, N-aryloxazolidinone, is not planar. The dihedral angles between the least-squares planes of the oxazolidine and phenyl rings are 52.7(5) and 39.0(6)° in two crystallographically independent molecules.

Process for preparing oxazolidine- and oxazolidinone-aminodiols

Abstract: A method of preparing oxazolidine-protected and oxazolidinone-protected aminodiol compounds is disclosed. These compounds tend to be useful as intermediates in processes for making Florfenicol and related compounds.

Total Synthesis of an Endothelin Converting Enzyme Inhibitor, TMC-66

Abstract: The first total synthesis and structural determination of TMC-66, an ECE inhibitor, was achieved in short steps by efficient construction of two tricyclic segments and coupling reactions. The oxidative coupling with phenols attaching to electron-withdrawing groups was realized with a novel copper (II) reagent.

1-(4-Methoxy-phen-yl)-7-phenyl-3-(phenyl-selenylmeth-yl)perhydro-isoxazolo[2',3':1,2]pyrrolo[3,4-b]azetidine-6-spiro-2'-chroman-2,4'-dione.

Abstract: In the title compound, C35H30N2O5Se, the pyrrolidine ring adopts an envelope conformation and the oxazolidine ring is in a twist conformation. The tetra­hydro­pyran ring adopts a half-chair conformation. The methoxy­phenyl ring is twisted away from the attached azetidinone ring by 15.7 (1)°. In the crystal structure, inter­molecular C—H⋯O inter­actions link the mol­ecules into a two-dimensional network.

Phenolic novolac foams and compositions for preparing them

Abstract: A foamable novolac phenolic resin composition suitable for preparing phenolic foams that are free of corrosive acid catalysts and excess aldehydes. The composition comprises a novolac resin, an oxazolidine hardener, and a blowing agent.

Carbohydrate-Based Spiro-1,3-oxazolidine-2-thiones : Stereoselective Approaches Using Aziridines and Epoxides

Abstract: D-glucose and D-fructose have been used as starting materials to prepare spiro-1,3-oxazolidine-2-thiones anchored on the third position of both carbohydrates. Following different approaches and depending on the carbohydrate template explored, stereoselective reactions have been developed via the formation of epoxides or aziridines.

Highly Diastereoselective Synthetic Route to Enantiopure β2-Amino Acids and γ-Amino Alcohols Using a Fluorinated Oxazolidine (Fox) as Chiral Auxiliary.

Abstract: The alkylation reactions of an amide enolate derived from a trifluoromethylated oxazolidine (Fox) chiral auxiliary occur with a complete diastereoselectivity and in good yields with various electrophiles. This reaction provides a versatile and straightforward strategy for the synthesis of β2-amino acids and γ-amino alcohols in enantiopure form.

Anti-microbial studies on novel 1,3-oxazolidine analogs

Abstract: In present study several substituted 1, 3-oxazolidines were synthesized by condensation of reduced Schiff base of phenylglycinol with different aldehydes. All the synthesized compounds showed good to moderate antimicrobial activity. The antimicrobial activites were performed by disc diffusion method and minimum inhibitory concentration determination by serial agar dilution method. Thus among the ten compounds, 3-[3-2- furyl methyl)-4-phenyl- 1,3-Oxazolidin-2-yl]-1H-indole (4a), 2-(2-furyl)-3-(2-furyl methyl)-4-phenyl-1,3-Oxazolidine (4b) and 4-[3-(2 furylmethyl)-4-phenyl-1,3- oxazolidin-2-yl]-2-methoxy phenol (4h) were found to have a moderate to significant antimicrobial activity against all the strains used. Compound 2-(4-chlorophenyl)-3-(2- furylmethyl)-4-phenyl-1, 3-oxazolidine (4j) showed very good antifungal activity than the other compounds tested. Further more, compounds containing -Cl-, -OCH3, -OH groups as substituents were found to be potent antimicrobial agents. Moreover the heteroaromatic substitutions also showed very good antimicrobial activities.

trans-4-(1-Naphth-yl)-2-oxo-1,3-oxazolidine-5-carboxylic acid.

Abstract: The crystal structure of the title compound, C14H11NO4, is influenced by N—H⋯O and O—H⋯O hydrogen bonds, linking mol­ecules into one-dimensional tapes running along the [010] direction.

(4S)-Benzyl 4-isopropyl-5-oxo-1,3-oxazolidine-3-carboxyl-ate.

Abstract: In the crystal structure of the title compound, C14H17NO4, obtained by the reaction of N-benzoxycarbonyl-l-valine, paraformaldehyde and 4-methyl­benzene­sulfonic acid, mol­ecules are linked by C—H⋯O hydrogen bonds, generating linear chains parallel to the a axis. C—H⋯π inter­actions of stacked benzene rings also provide stability for the crystal structure.

Highly Enantioselective Alkynylation of Aldehydes Catalyzed by a New Oxazolidine—Titanium Complex.

Abstract: The readily available and inexpensive new chiral oxazolidine in combination with Ti(O(i)Pr)(4) was found to catalyze the reaction of an alkynylzinc reagent with various types of aldehydes to generate chiral propargylic alcohols with high enantioselectivities (up to 95%) and excellent yields (up to 98%).