H. Takayanagi et al., A KETAL CLAISEN REARRANGEMENT FOR ALPHA-KETOL ISOPRENE UNIT ELONGATION - APPLICATION TO A PRACTICAL SYNTHESIS OF SARCOPHYTOL-A INTERMEDIATE, Journal of the Chemical Society. Perkin transactions. I, (7), 1995, pp. 751-756
A new ketal Claisen rearrangement using the ketal 10 for the isoprene
unit elongation which affords terminal alpha-ketol terpenoid is presen
ted. Its efficiency is demonstrated by successful transformation of th
e product of this reaction, the alpha-ketol 20, into 2, the acyclic pr
ecursor of sarcophytol A total synthesis, by two alternative routes vi
a the beta,gamma-unsaturated aldehyde 24 and the allylic alcohol 28.