Stereospecific intramolecular Michael addition to (-)-carvone based on temporary sulfur connection

Article abstract of DOI:10.1016/S0040-4039(98)00327-X

An acetic acid residue (CH₂CO₂Me) was stereoselectively attached to (- )-carvone (7) to give (1R,2S,5R)-(5-isopropenyl-2-methyl-3- oxocyclohexyl)acetic acid methyl ester (21) in a process involving the following stages: i) addition of ClSCH₂CO₂Me to the isopropenyl group of 7 to give, after oxidation, [1-chloro-2(RS)-(l(R),4-methyl-5-oxocyclohex-3- enyl)propane-2-sulfonyl]acetic acid methyl ester (18); ii) intramolecular Michael addition of 18 to afford (1S,2S,4(RS),5R,8S)-4-chloromethyl-4,8- dimethyl-3,3,7-trioxo-3-thiabicyclo [3.3.1]nonane-2-carboxylic acid methyl ester (20); iii) disconnection of the acetic acid moiety by a tandem reductive elimination involving sulfur extrusion and restoration of the isopropenyl group (20 → 21).