Improved synthesis of vitamin K_1

摘要

With (E/Z)-isomeric phytyl halides as side-chain materials, vitamin K_1 is synthesized via a Diels-Alder reaction to activate the free bridgehead hydrogen of 3 for the alkylation and a retro-Diels-Alder reaction to eliminate cyclopentadiene from 2 in a high yield, in which the configuration of the double bond in the phytyl side-chain is retained.