Improved preparation of 9,10,12,13‐tetrahydroxystearic acids fromanti‐cis,cis‐9,10,12,13‐diepoxystearic acid

Abstract

A mixture of isomeric 9,10,12,13-tetrahydroxystearic acids (threo, threo, threo and threo, erythro, threo) can be prepared from anti-cis, cis-9,10,12,13-di-epoxystearic acid in over 80% yield by way of the intermediate di(hydroxy-alkoxysulfonium) salts and in ca. 68% yield by way of the intermediate di(hydroxy-formate) esters obtained by acid-catalyzed epoxide ring opening with dimethyl sulfoxide and formic acid, respectively. Mechanisms and stereochemistry of formation of the two isomers are discussed. Factors that influence the formation of cyclic products in competition with tetrahydroxystearic acids also are described. The key to the greatly improved yield of tetrahydroxystearic acids over prior literature procedures is avoiding water during ring opening of the protonated epoxide, as even small quantities of water cause marked reduction in yields of tetrahydroxystearic acids.

Hyperbranched polyesters by polycondensation of fatty acid-based ABn-type monomers

“…The low yield in the latter case could be explained by the hydroxylation of methyl ricinoleate which resulted in a mixture of four diastereoisomers, only one of them being able to crystallize. [42][43][44][45] The structure of the so-formed AB 2 -or AB 3 -type monomers was assessed by 1 H NMR spectroscopy (see ESI Figure S1). GC analyses revealed a chemical purity higher than 94% in all cases.…”