ChemInform Abstract: Methyl Jasmonate: A Short Synthesis of Naturally Occurring Methyl Jasmonate and Its Unnatural Enantiomer via Enantiodivergent Alkylation of Cyclopent‐2‐ene‐1,3‐diol Derivatives by Palladium(0)‐Induced Reactions.

Abstract

Palladium‐catalyzed alkylation of the cyclopentenediol derivative (I) is a useful method for enantiodivergent functionalization resulting in both enantiomeric series (III) and (XII) of chiral building blocks.

Enantioselective Synthesis of Both Enantiomers of Dimethylcis-(4-Acetoxycyclopent-2-enyl)malonate, Key Intermediates for Epijasmonate

“…The spectral data of 3 and 8 (IR, 1 H, and 13 C-NMR) were identical with those reported in the literature. 4) In summary, the synthesis of both enantio-enriched intermediates for epijasmonoid was achieved. Although the enantiomeric purity of 3 and 4 was not su‹ciently high, we could easily obtain both enantiomers in an enantio-enriched form by starting from common substrate 2 and only changing the chirality of the ligand.…”

“…The enantiomeric purity was determined by comparing the [a]D value with that reported in the literature. 4) The same reaction gave only 19z and 23z ee of 3 by the use of (R)-(S )-BPPFA and (R)-(+)-BINAP as ligands, respectively (Table 1). On the other hand, by the same method, enantiomer 4 was obtained by the use of (1S,2S )-7 as a ligand.…”

“…3) Montforts et al have reported that the synthesis of both enantiomers of cis-jasmonate (epijasmonate 1 and its enantiomer 9) by enzymatic desymmetrization of meso-diacetates 2 and subsequent stereospeciˆc palladium-catalyzed allylic alkylation. 4) Although a highly enantioselective synthesis of 1 and 9 was achieved, synthesis of the natural isomer (3R,7S-isomer 1) needed extra manipulation by introducing a reactive leaving group for the metal-catalyzed reaction. 4) We now report a more straightforward method for the synthesis of both enantiomers (3 and 4) of dimethyl cis-(4-acetoxycyclopent-2-enyl)malonate, known intermediates for epijasmonate, 4) by direct asymmetric alkylation of meso-diacetate 2 5) with chiral palladium-phosphine catalysts.…”

“…On the other hand, by the same method, enantiomer 4 was obtained by the use of (1S,2S )-7 as a ligand. As malonate derivative 4 could not be found in the literature, 4) it was converted into known alcohol 8, a precursor of ent-epijasmonate 9 (3S,7R-isomer), by mild hydrolysis with triethylamine as a base in aqueous methanol in a 75z yield and 84z ee. The spectral data of 3 and 8 (IR, 1 H, and 13 C-NMR) were identical with those reported in the literature.…”

“…Although the enantiomeric purity of 3 and 4 was not su‹ciently high, we could easily obtain both enantiomers in an enantio-enriched form by starting from common substrate 2 and only changing the chirality of the ligand. It is well known that cis-isomers 1 and 9 can be easily isomerized to trans-isomers, so all four stereoisomers of jasmonoid would be available by combining our and the literature procedures 4) from a common starting material.…”