Chemistry and Stereochemistry of Iridoids, XIII. — Synthesis of Enantiomerically Pure Methyl (1R,2S,2″Z)‐(+)‐Jasmonate Starting from Catalpol Enantiomerically pure methyl (1R,2S,2″Z)‐(+)‐jasmonate (2), which was recognized as a component of the fragrance of the jasmine flower oil, was synthesized starting from catalpol (3). 2 is easily epimerized to 1. Thus, it is necessary to use very mild conditions in the course of the synthesis and purification. These results raise the question whether 2 exists as a natural product in the flower of jasmine and 1 arises during the isolation.

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298ChemInform Abstract Whereas first of all (-)-methyljasmonate (XII) had been regarded as the characteristic fragrance of the jasmine flower oil, later reports (Nishida et al., 1985; Weinges et al., 1987) have demonstrated the (+)-diastereomer (XI) to be the real scent. With regard to recently published stereoselective syntheses of (XI), the authors now announce their own procedure. Key step is the Wittig homologation reaction of (II) (prepared from catalpol (I) as already reported (1987)) to give (IV) with a latent aldehyde group to introduce the missing rest of the side chain by a second Wittig reaction. The (+)-isomer (XI) is easily epimerized to (-)-(XII) even on normal silica gel used for chromatography.