The SAMP-/RAMP -hydrazone methodology in asymmetric synthesis of 4S-ferrugineone and 4S, 5S-ferrugineol: The pheromones of palm weevils

4S-ferrugineone and 4S,5S-ferrugineol as pheromones of palm weevils were synthesized in 3 and 4 steps, respectively, starting from nonane-5-one employing SAMP-/RAMP -hydrazone methodology. 5-nonanone is transformed to its corresponding RAMP hydrazone by reaction with the enantiomerically pure hydrazine RAMP. Metalation with lithium diisopropylamide (LDA) in ether to form azaenolate, followed by methylation with methyl iodide, furnishes the product hydrazone. Finally, cleavage of the hydrazone moiety to regenerate the carbonyl functionality is possible by ozonolysis, leads to the 4S-ferrugineone. The crucial step would be the final diastereoselective reduction to the 4S, 5S-ferrugineol.The 4S, 5S-ferrugineol has been obtained with better yield (71%) and good disteromeric excess 40% de at -78 °C.