Regio- and enantio-selective photodimerisation of cyclohex-2-enone as an inclusion complex with a new optically active host, (–)-1,4-bis[3-(o-chlorophenyl)-3-hydroxy-3-phenylprop-1-ynyl]benzene: preparation of the optically pure (–)-syn-trans-dimer of cyclohex-2-enone

1992 ◽  
pp. 307-307 ◽  
Author(s):  
Koichi Tanaka ◽  
Osamu Kakinoki ◽  
Fumio Toda
Keyword(s):  
Inclusion Complex ◽  
Optically Active ◽  
Optically Pure ◽  
Trans Dimer

Synthesis and resolution of an asymmetric arsonium cation. Crystal and molecular structures of (R)-Benzyl(methyl)(4-methylphenyl)(naphthalen-1-yl)- arsonium bromide and hexafluorophosphate

1984 ◽  
Vol 37 (6) ◽  
pp. 1171 ◽  
Author(s):  
DG Allen ◽  
CL Raston ◽  
BW Skelton ◽  
AH White ◽  
SB Wild
Keyword(s):  
Ion Exchange ◽  
Absolute Configuration ◽  
Optically Active ◽  
Molecular Structures ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
X Ray ◽  
Crystal And Molecular Structures ◽  
Ion Exchange Column ◽  
Optically Pure

The (�)-benzyl(methyl)(4-methylphenyl)(naphthalen-1-yl)arsonium cation has been synthesized and subsequently resolved by fractional crystallization of monohydrogen [R-(R*,R*)]-2,3-bis(benzoyloxy)- butanedioate salts. The separated diastereoisomers were converted into the corresponding optically active arsonium bromides by ion-exchange column chromatography. The absolute configuration of the arsonium cation exhibiting a positive rotation at 589 nm (sodium D line) has been established as (R) by single-crystal X-ray analysis of both the bromide and hexafluorophosphate salts. The arsonium bromide with [α]D + 54.8�(c, 0.62 in CH2Cl2) crystallizes in the orthorhombic space group P212121 (D24, No.19) with a 22.472(8), b 15.724(7), c 12.585(5) � and U 4447(3) �3. The corresponding hexafluorophosphate with [α]D + 19.3� (c, 0.5 in CH2Cl2) crystallizes in the same space group with a 23.56(2), b 16.40(1), c 13.12(1) � and U 5067(6) � 3. Benzylidene transfer to benzaldehyde from the arsonium ylide derived from either of the arsonium salts produced optically pure (–)-(S)-methyl(4-methylphenyl)(naphthalen-1-yl)arsine, [α]D - 115.9� (c, 0.593 in CHCl3), and partly resolved [R-(R*,R*)]-2,3-diphenyloxiran.

Preparation of secondary alcohols of high optical purity

1986 ◽  
Vol 51 (2) ◽  
pp. 401-403 ◽  
Author(s):  
Otakar Červinka ◽  
Anna Fábryová ◽  
Irina Sablukova
Keyword(s):  
Nmr Spectroscopy ◽  
Optical Purity ◽  
Optically Active ◽  
Secondary Alcohols ◽  
Lithium Aluminium Hydride ◽  
Enantioselective Reduction ◽  
H Nmr ◽  
Lithium Aluminium ◽  
High Optical Purity ◽  
Optically Pure

Partially resolved enantiomers of optically active alcohols I-V, obtained by enantioselective reduction of the corresponding ketones with lithium aluminium hydride in the presence of (-)-quinine, were converted into crystalline 3,5-dinitrobenzoates or phenylcarbamates. The esters of the nearly optically pure enantiomers were separated by crystallization from the generally more soluble esters of the racemates. Optical purity of the hydrolytically liberated alcohols was determined by 1H NMR spectroscopy in the presence of chiral shifting agents.

Synthesis of Optically Active N6-Alkyl Derivatives of (R)-3-(Adenin-9-yl)-2-hydroxypropanoic Acid and Related Compounds

2003 ◽  
Vol 68 (5) ◽  
pp. 931-950 ◽  
Author(s):  
Marcela Krečmerová ◽  
Miloš Buděšínský ◽  
Milena Masojídková ◽  
Antonín Holý
Keyword(s):  
Nmr Spectra ◽  
Enantiomeric Purity ◽  
Optically Active ◽  
Secondary Amines ◽  
H Nmr ◽  
Alkyl Derivatives ◽  
Optically Pure ◽  
Derivatives Of ◽  
Related Compounds

Reaction of ethyl (R)-oxiranecarboxylate (2a) with various nucleobases (adenine, 6-chloropurine, thymine, cytosine, N6-benzoyladenine, 4-methoxy-5-methylpyrimidin-2(1H)-one and 4-methoxypyrimidin-2(1H)-one) afforded ethyl 3-substituted-2-hydroxypropanoates 4-10. Enantioselectivity of this reaction is dependent on the type of the base: 6-chloropurine, N6-benzoyladenine, 4-methoxy-5-methylpyrimidin-2(1H)-one, thymine and cytosine gave optically pure R enantiomers. In other cases, partial or complete racemization occurred. Optically pure ethyl (R)-3-(6-chloropurin-9-yl)-2-hydroxypropanoate (5a) was hydrolyzed to give (R)-3-(6-chloropurin-9-yl)-2-hydroxypropanoic acid (11). Reactions of 11 with various primary or secondary amines led to N6-substituted (R)-3-(adenin-9-yl)-2-hydroxypropanoic acids 14-19. Enantiomeric purity was determined from 1H NMR spectra measured in the presence of (-)-(R)-1-(9-anthryl)-2,2,2-trifluoroethan-1-ol.

scholarly journals New routes to chiral phosphines

1985 ◽  
Author(s):  
Άγγελος Βουγιούκας
Keyword(s):  
Dicarboxylic Acid ◽  
Phosphine Oxide ◽  
Experimental Error ◽  
Phosphonium Salt ◽  
Optically Active ◽  
Side Chain ◽  
Phosphonium Salts ◽  
Unstable Compound ◽  
Chiral Phosphines ◽  
Optically Pure

The reaction of diphenyl(2-trimethylsilylethyl)phosphine with methyl trifluoromethanesulphonate gave a phosphonium salt from which the side-chain was cleaved with F ® , yielding diphenylmethylph osphine. A slower reaction with the triphenylsilyl-analogue gave the corresponding phosphine oxide. When the cleavage of a diphosphonium salt was attempted the product was a mixture of 1,3-bis-(diphenylphosphino)propane and diphenyl(2-trimethylsilylethyl)phosphine in 1:2 ratio showing the cleavage to be unselective. ß-Silylphosphonium salts derived from 2,2-dimethyl-H-methylene- 1 , 3-dioxolane reacted with F® to provide completely selective cleavage of the dioxolanyl side-chain, and a related bis-phosphonium salt gave only diphenyl(2-trimethylsilylethyl)phosphine under similar conditions. Greater selectivity towards fragmentation of the silylated side-chain was achieved with triethoxysilylethyl derivatives and 1, 3-bis-(diphenylphosphino)propane as well as 1,4-bis-(diphenylphosphino)butane were prepared in this way, in 86% and 9^% yield respectively. It was found that the dioxolanylmethyl side-chain was more readily cleaved from phosphonium salts than was 2-(triethoxylsily1)ethyl, however. In similar manner, reaction of 2-(trimethylsilyloxyethy1)- methyldiphenylphosphonium trifluoromethanesulphonate with Fö gave methyldiphenylphosphine oxide. The same reaction occurred when the corresponding hydroxyethylphosphine was treated with KH. This method was shown to be applicable to the synthesis of biphosphine oxides. Nevertheless, application to dioxolanylmethyl phosphonium salts again led to px^ef erential loss of that side-chain; this caused a change to utilisation of the trans-1,2-dimethylcyclobutyl backbone. The optically active o-anisylmethylphenylphosphine oxidewas prepared in both enantTomeric forms by a literature route. Reaction of the R-isomer with (iPr)2NLi and then acetone led to a new phosphine oxide which was reduced with E t 3N/Cl3$iH and reacted with methyl trifluoromethanesulphonate to giveR - (2-hydroxy-2-methylpropyl)(o-methoxyphenyl)methylphenylphosphonium trifluoromethanesplphonate. This reacted with KH to give the parent phosphineOKas R-enantiomer, optically pure within experimental error. “ A new route for the resolution of trans-cyclobutane-1,2-dicarboxylic acid has been developed. This involved the preparation of the bis-ephedrinium amide and its separationinto diastereomers by silica chromatography. The enantiomers were converted into SS and RR t r a n s - 1 ,2-cyclobutanedimethanolof 100% and 88% optical purTTy respectively. Whilst it proved possible to prepare the racemic bis-trifluoromethanesulphonate, it was an unstable compound and the optically active analogues could not be isolated in several attempts.

scholarly journals Bienzymatic Cascade for the Synthesis of an Optically Active O-benzoyl Cyanohydrin

Catalysts ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 522 ◽  
Author(s):  
Laura Leemans ◽  
Luuk van Langen ◽  
Frank Hollmann ◽  
Anett Schallmey
Keyword(s):  
Organic Solvent ◽  
Manihot Esculenta ◽  
Direct Synthesis ◽  
Enantiomeric Excess ◽  
Candida Antarctica ◽  
Optically Active ◽  
Candida Antarctica Lipase ◽  
Hydroxynitrile Lyase ◽  
Lipase A ◽  
Optically Pure

A concurrent bienzymatic cascade for the synthesis of optically pure (S)-4-methoxymandelonitrile benzoate ((S)-3) starting from 4-anisaldehyde (1) has been developed. The cascade involves an enantioselective Manihot esculenta hydroxynitrile lyase-catalyzed hydrocyanation of 1, and the subsequent benzoylation of the resulting cyanohydrin (S)-2 catalyzed by Candida antarctica lipase A in organic solvent. To accomplish this new direct synthesis of the protected enantiopure cyanohydrin, both enzymes were immobilized and each biocatalytic step was studied separately in search for a window of compatibility. In addition, potential cross-interactions between the two reactions were identified. Optimization of the cascade resulted in 81% conversion of the aldehyde to the corresponding benzoyl cyanohydrin with 98% enantiomeric excess.

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