Direct catalytic enantioselective cross aldol-typereaction of an acetate surrogate was developed using Cu alkoxide-chiral phosphine complexes as catalysts. Chemoselective activation and deprotonation of the donor substrate (acetonitrile) by the soft metal alkoxide in a strongly donating solvent (HMPA) are key to success in this reaction. Useful chemical yields and promising enantioselectivities are
Organocatalysed synthesis of isoxazolines initiated by a chemoselective oxa-Michael reaction of N-BocNHOH
作者:R. Noël、V. Gembus、V. Levacher、J.-F. Brière
DOI:10.1039/c3ob42406e
日期:——
An organocatalysed and chemoselective one-pot oxa-Michael-cyclocondensation reaction of N-BocNHOH to unsaturated α-ketoesters is reported which affords an original entry to enantioenriched 3-isoxazoline carboxylate derivatives as biorelevant heterocyclic frameworks.
Totalsynthesis of mevinicacidanalog 1 has been achieved efficiently starting from chiral 2,3‐O‐isopropylidene‐D‐glyceraldehyde (2). The synthesis involves Mitsunobu reaction and Evans' intramolecular oxa‐Michael syn‐addition reactions as key steps.
Enhanced enantioselectivity of an enzymatic reaction by the sulfur functional group. A simple preparation of optically active .beta.-hydroxy nitriles using a lipase
The enantioselectivity of a lipase-catalyzed hydrolysis was improved by varying the acyl residue into the sulfur functional one, i.e. the beta-(phenylthio)- or beta-(methylthio)acetoxy group, from acetate or valerate to realize satisfactory resolution of beta-hydroxy nitriles using lipase P (Pseudomonas sp.).