The prevalence of natural 3-alk(en)yl-substituted phenols and their potential semisyntheses from cashew nut shell liquid
The focus of this mini-review is to assemble an instructive sample of natural products possessing structural features present in phenolic constituents of Cashew Nut Shell Liquid (CNSL) and, thus, inspire researchers to undertake semisyntheses of these natural products using the relatively abundant phenolic components of CNSL as raw materials. In this review, the author attempts to identify (or point out to) a 3-alk(en)yl-substituted phenolic sub-structure embedded in a particular natural product and reveal the CNSL phenolic component that has the corresponding structural motif. In addition, the author prompts the reader into a thinking process that should eventually lead him/her to developing a comprehensive retrosynthesis of a particular natural product culminating to that CNSL phenolic component as the starting material. Thus, in some way this paper is a tutorial review to the newcomers in the field of natural product synthesis utilizing natural resources. The seasoned synthetic chemists will also benefit from this collection as they guide and inspire their research trainees to take up natural product synthesis. In this article, a
brief introduction to the composition and applications of CNSL is presented. This is followed by a compilation from the literature of reported natural products possessing the 3-alk(en)yl-substituted phenolic moiety. Alongside this compilation, a diagnostic discussion is presented aiming at pinpointing CNSL phenols as prospective precursors for the semisyntheses of some selected natural products as illustrative examples.
Key words: Semisynthesis, CNSL phenols, 3-alk(en)yl-substituted phenolic sub-structure, natural products synthesis, natural resources