Abstract: The marine peptides have been a fertile source for new bioactive molecules, and many possess potent activity, across a broad spectrum of targets. Their diversity in both biological activity and in chemical complexity has made these secondary metabolites being the focus of much work in recent years. As a fragment, (R)-2-methyloctanoic acid-7-yne was always found in those nature materials. In this article, (R)-2-methyl-7-octynoic acid was synthesized with pentane-1,5-diol as the start material. Stereogenic carbon(C-2) was obtained through alkylation induced with Evans' chiral auxiliary, and alkyne 13 was got by use of Ohira-Bestmann reagent. Through 13-step reactions the target molecule was prepared with over yield of 17.1%, and e.e. beyond 99%.

Key words: (R)-2-methyl-7-octynoic acid, Unsymmetrical alkylation, Ohira-Bestmann reagent