Total Synthesis and Determination of Absolute Configuration of Cryptorigidifoliol G.

The first asymmetric total synthesis of (1 S ,5 R ,7 S )-cryptorigidifoliol G and (1 S ,5 R ,7 R )-cryptorigidifoliol G of the proposed natural product was achieved. The key steps in the synthesis involved Keck-Maruoka allylation, our own developed protocol for the construction of the trans -2,6-disubstituted dihydropyran, iodolactonization, cross-metathesis, Prins cyclization, and cis -Wittig olefination reaction. A comparison of the NMR as well as analytical data and thorough analysis of the 2D NMR suggested that the absolute stereochemistry of the proposed natural product is (1 S ,5 R ,7 S )-cryptorigidifoliol G.