A SHORT AND STEREOSELECTIVE SYNTHESIS OF THE (+/-) PRELOG-DJERASSI LACTONIC ACID

Article abstract of DOI:10.1016/S0040-4039(01)82113-4

Reaction of meso-4-carbomethoxy-2-methylpentanal (1) with crotyltri-n-butyltin at -78 deg C in the presence of 1 eq BF3*OEt2, followed by the lactonization with BF3*OEt2, gave 6-(1-methylallyl)-3,4,5,6-tetrahydro-3,5-dimethyl-2-pyranone (2a) with the correct stereochemistry (erythro, anti-Cram) in 92percent yield, which was converted to the title compound (3) in 85percent yield upon the ozonolytic cleavage of the double bond.