Synthesis of the monoterpenoid esters cypellocarpin C and cuniloside B and evidence for their widespread occurrence in Eucalyptus

Short syntheses of cuniloside B and cypellocarpin C, (+)-(R)-oleuropeic acid-containing carbohydrates, are reported. Also disclosed are syntheses of the noreugenin glycosides, undulatoside A and corymbosins K1 and K2. Leaf extracts of 28 diverse eucalypts revealed cuniloside B to be present in all, and cypellocarpin C to be present in most, of the species examined. The widespread occurrence of these carbohydrate monoterpenoid esters supports their roles in essential oil biosynthesis or mobilization from sites of synthesis to secretory cavity lumena.

Graphical abstractThe total synthesis of several carbohydrate noreugenin glycosides and monoterpenoid esters is reported. Two of these, cypellocarpin C and cuniloside B, are found as constituents of a wide range of Eucalyptus.Figure optionsDownload full-size imageDownload as PowerPoint slide