Abstract
We have developed various effective methods for the synthesis of natural products. Two topics have been reviewed from our recent achievement. The first topic describes new synthetic methods based on the chemistry of allenylmethyltrimethylsilanes. The synthetic utility has been demonstrated in the syntheses of L-arcanose (19), L-olivomycose (21), a key synthetic precursor of antitumor anthracyclines 23, (-)-paeoniflorin (28), (+)-allokainic acid (56), and (-)-kainic acid (61). The second topic describes new methodology utilizing the Katsuki-Sharpless reaction. Based on titanium-tartrate mediated asymmetric epoxidation of prochiral σ-symmetrical divinylcarbinols, (+)-endobrevicomin (69), (-)-exobrevicomin (71), D-olivose (77), D-oleandrose (78), D-digitoxose (79), D-cymarose (80), (-)-citreoviridin (86), and (+)-verrucosidin (87) have been synthesized enantioselectively. A new practical method for the preparation of polyol chiral building blocks has been developed based on the Red-Al promoted intramolecular reductive cleavage of the epoxy alcohol 98 available from the divinylcarbinol 97. The synthetic utility of this method has been demonstrated by an expeditious synthesis of the compactin lactone 110. Lewis acid mediated cyclization using a chiral epoxy alcohol as an initiating functionality has also been developed. (+)-Brefeldin A (129) and a key C/D-ring synthon of vitamin D 135 have been prepared using this methodology.
