Two new methods for the determination of the absolute configuration of methyl 4-methyl-6-(2-methylprop-1-enyl)cyclohexa-1,3-dienecarboxylate are proposed, and the configurations attributed previously to its (+)- and (-)-enantiometers are confirmed. Chiral methyl carboxylate is converted into the corresponding alcohol whose configuration is deduced from either the rate of hydrolysis of the respective racemic acetate in the presence of pancreatic lipase (method I) or from the difference between the Eu(fod)(3)-induced shifts of the MeO signals in the H-1 NMR spectra of the diastereomeric esters of S- or R-Mosher's acid (method 2).
Catalytic asymmetric synthesis of polysubstituted cyclohexa-1,3-dienes from ?-branched ?,?-alkenals
作者:A. G. Nigmatov、E. P. Serebryakov
DOI:10.1007/bf01435793
日期:1996.3
°C to give optically active esters of 4,6-disubstituted cyclohexa-1,3-diene-l-carboxylic acids in moderate (10–43 %) yields. The enantiomeric purity of the products formed from the lint two types of acidic ylidenemalonates varies from 28 to 68 % and is higher than that observed in the case of related alkylidenemalonates. Under similar conditions cyclohexylideneacetaldehyde affords optically active derivatives