Novel synthesis of chiral, enantiomerically pure thiodiglycols and diglycols
作者:Jens Christoffers、Ulrich Rößler
DOI:10.1016/s0957-4166(98)00224-9
日期:1998.7
converted in a sequence of O-protection, reduction, O-activation, thioether and ether formation and deprotection to chiral, non-racemic β,β′-dihydroxy thioethers 1a, 1b and ether 1c. Overall yields are excellent (75%). In an attempt to synthesize the respective dihydroxy ether 1d derivedfrom mandelic acid 1,3-dioxolane derivatives 7 were obtained.
Enzymatic resolution of propylene glycol alkyl (or aryl) ethers and ether acetates
申请人:Resnick M Sol
公开号:US20050026260A1
公开(公告)日:2005-02-03
Glycol ether acetates, and in particular propylene glycol alkyl (or aryl) ether acetates, can be resolved enzymatically by enantioselective hydrolysis with a hydrolase at high concentrations of substrates; in some embodiments, the hydrolase is a lipase. Glycol ethers, and in particular propylene glycol alkyl (or aryl) ethers, can be resolved enzymatically by enantioselective transesterification with a hydrolase, in the presence of an acyl donor, at high concentrations of substrates; in some embodiments, the hydrolase is a lipase.
Chiral Pyridine-Based Macrobicyclic Clefts: Synthesis and Enantiomeric Recognition of Ammonium Salts
作者:Paul C. Hellier、Jerald S. Bradshaw、J. Jolene Young、Xian Xin Zhang、Reed M. Izatt
DOI:10.1021/jo960890u
日期:1996.1.1
An achiral (3) and two chiral pyridine-based macrobicyclic clefts (4 and 5) have been prepared by treating 2,6-bis[[2',6'-bis(bromomethyl)-4'-methylphenoxy]pyridine (2) with the appropriate achiral and chiral glycols. Starting 2 was prepared by first treating 2,6-bis(hydroxymethyl)-4-methylphenol with 2,6-[(tosyloxy)methyl]pyridine followed by phosphorus tribromide. Achiral macrobicyclic cleft 3 formed a complex at 25 degrees C in 50% CH3OH/50% CHCl3 (v/v) with a primary ammonium salt (log K=3.15) as evidenced by a significant change in the (1)HNMR spectrum. Highly organized (S,S,S,S)4, prepared by treating 2 with (1S,5S)-3-oxapentane-1,5-diol, exhibited recognition at 25 degrees C in 20% C2H5OH/80% 1,2-C2H4Cl2 (v/v) for the (S)-enantiomer of alpha-(1-naphthyl)-ethylammonium perchlorate (NapEt) over its (R)-form (Delta log K=0.85). This high recognition factor probably reflects an increase in molecular rigidity by the introduction of a second macro ring on the monocyclic pyridinocrown ligand.
One-Pot Generation and Conversion of Trichloroacetimidates for the Racemization-Free Allylation and Benzylation of α-Hydroxyesters and the Enantiopure Synthesis of a Chiral Diglycole
O-Allylations and O-benzylations of alpha -hydroxy esters (3a-3c) are performed without racemization. The reagents applied, O-allyl- and O-benzyltrichloroacetimidate (5a, 5b) are prepared and converted in a one-pot-procedure. After protection by benzylation (S)-(-)-ethyl lactate (3a) is converted by a sequence of carbonyl reduction, alcohol activation, ether formation, and deprotection to the optically active diglycole derivative 1a.
Mono- and Bidentate Phosphinanes—New Chiral Ligands and Their Application in Catalytic Asymmetric Hydrogenations