SYNTHESIS OF MEDIUM AND LARGE RING COMPOUNDS .39. STEREOSELECTIVE SYNTHESIS OF BOTH ENANTIOMERS OF 13-TETRADECANOLIDE BY RING ENLARGEMENT WITH DIFFERENT CHIRAL BUILDING-BLOCKS AND OLFACTORY COMPARISON WITH (12R)-(-12-METHYL-13-TRIDECANOLIDE AND (12S)-(-)-12-METHYL-13-TRIDECANOLIDE())

Starting from a cycloalkanone and the chiral building blocks 2 or 3 bo th enantiomers of 13-tetradecanolide (1, n = 14) were prepared by ring -enlargement reactions. Cycloudecanone (4) was alpha-alkylated with th e protected hydroxy halide 2 derived from (S)-(-)-methyl lactate. Acid -catalyzed cyclization, oxidative cleavage of the enol ether double bo nd by PCC, and reduction of the carbonyl group via a tosylhydrazone le d to the (S)-configured target molecule (+)-8 (98.0% ee), thus indicat ing the sequence proceeded with clean retention of configuration. Like wise, the naturally occurring (R)-enantiomer (-)-8 (>99.8% ee) was syn thesized from cyclodecanone (9) and the chiral building block 3. Aided by CD conformational analysis the olfactory properties of both enanti omers were compared with those of the regioisomers (12R)-(+)- and (12S )-(-)-12-methyl-13-tridecanolide previously prepared by the same metho d.