HIGHLY STEREOSELECTIVE SYNTHESIS OF TRISUBSTITUTED GAMMA,DELTA-UNSATURATED ACID AND ALDEHYDE VIA KETAL CLAISEN REARRANGEMENT

A new sequence for the highly stereoselective (E>99%) synthesis of a t risubstituted gamma,delta-unsaturated acid (3), which consists of a ke tal Claisen rearrangement of a terpene allylic alcohol with 2,2-dimeth oxy-3-methyl-3-butanol and a subsequent oxidative cleavage of the resu lting alpha-ketol, is applicable even to the preparation of 3 which is difficult to synthesize by traditional methods. The related procedure for preparation of the corresponding aldehyde is also described.