3-Hydroxy-2-methyl-and 3-hydroxy-2,4-dimethyl-substituted long-chain carboxylic esters

Abstract

3-Hydroxy-2-methyl- and 3-hydroxy-2,4-dimethyl-substituted long-chain carboxylic esters have been prepared by routes involving (i) reduction of the corresponding keto-esters, and (ii) Reformatsky reaction between the appropriate aldehydes and ethyl α-bromopropionate. The resulting 2,3-erythro- and threo-isomers of ethyl 3-hydroxy-2-methyleicosanoate, and of methyl and ethyl 3-hydroxy-2,4-dimethyldocosanoate have been separated by chromatography. High resolution i.r. studies of these esters are described, and n.m.r. data for the ethyl esters are also reported and discussed. The diastereoisomers of 1,3-dihydroxy-2-methyldocosane, obtained as by-products, were separated by preparative layer chromatography, and converted into the corresponding ethylidene acetals. High-resolution i.r. studies of the diols, and n.m.r. data for the diols and their acetals are reported.The conversion of ethyl 3-hydroxy-2,4-dimethyldocosanoate into trans- and cis-αβ-unsaturated esters was also studied. The resulting methyl trans- and cis-2,4-dimethyldocos-2-enoates were separated and identified by their u.v. and n.m.r. spectra.