Total Synthesis of (+/-)-Dimethyl Jaconate

Article abstract of DOI:10.1021/jo00257a002

The total synthesis of a cyclic necic acid derivative, (+/-)-dimethyl jaconate, is described as a seven-step sequence starting from 3,4-dichloro-2-furoic acid.The key step involves an intramolecular cycloaddition of furfuryl allyl sulfide 21b, establishing the desired relative stereochemistry of the three asymmetric centers on the tetrahydrofuran ring.The 1,2-dichloro olefin thus produced is uncovered as a diester equivalent through an ozonolysis reaction in methanol.Raney nickel desulfurization then reduces the linking sulfur bridge to produce the desired target, though as an epimeric mixture at the C6 hydroxyethyl center.This problem is addressed with a study of the stereoselective reductions of intermediate ketones 24 and 25, with the latter ketone affording a 4:1 ratio of products favoring the desired epimer.