Synthesis of medium and large ring compounds, XXXIX. Stereoselective synthesis of both enantiomers of 13‐tetradecanolide by ring enlargement with different chiral building blocks and olfactory comparison with (12R)‐(+)‐ and (12S)‐(−)‐12‐methyl‐13‐tridecanolide

Abstract

AbstractStarting from a cycloalkanone and the chiral building blocks 2 or 3 both enantiomers of 13‐tetradecanolide (1, n = 14) were prepared by ring‐enlargement reactions. Cycloundeca‐none (4) was α‐alkylated with the protected hydroxy halide 2 derived from (S)‐(−)‐methyl lactate. Acid‐catalyzed cyclization, oxidative cleavage of the enol ether double bond by PCC, and reduction of the carbonyl group via a tosylhydrazone led to the (S)‐configured target molecule (+)‐8 (98.0% ee), thus indicating the sequence proceeded with clean retention of configuration. Likewise, the naturally occurring (R)‐enantiomer (−)‐8 (>99.8% ee) was synthesized from cyclodecanone (9) and the chiral building block 3. Aided by CD conformational analysis the olfactory properties of both enantiomers were compared with those of the regioisomers (12R)‐( + )‐ and (12S)‐(−)‐12‐methyl‐13‐tridecanolide previously prepared by the same method.