A new practical synthesis of (+)-grandisol from (+)-citronellol using an intramolecular carbenoid cyclization

Abstract

A new practical 10 step synthesis of (1S,2R)-2-acetyl-1-methylcyclobutaneacetic acid 15 is reported, which has as a key step a rhodium catalyzed intramolecular carbenoid cyclization of the α-diazo-β-ketosulfone 5, readily available from (+)-citronellol 2. Since 15 has already been converted into (+)-grandisol 1, the major pheromone of the cotton boll-weevil Anthonomus grandis, the described preparation constitutes a new formal synthesis of the optically active pheromone.