Studies on monoterpene glucosides and related natural products. LV. Iridane skeleton formation from acyclic monoterpenes in the biosynthesis of iridoid glucosides in Gardenia jasminoides f. grandiflora cell suspension cultures.

Administration of 3H- or 13C-labeled acyclic monoterpenes to Gardenia jasminoides f. grandiflora cell suspension cultures showed that tarennoside (20) and gardenoside (21) were biosynthesized in the cell cultures via the cyclization of 10-oxogeranial (5a)/10-oxoneral (5b) to iridodial cation (14). followed by extensive randomization of the carbon atoms 3 and 11. Furthermore, the intermediacy of (R)-(+)-and (S)-(-)-10-hydroxycitronellol (24a, 24b) and (R)-(+)-and (S)-(-)-9, 10-dihydroxycitronellol (28a, 28b) was disproved.