Syntheses of (+)‐(S,S)‐(cis‐6‐Methyltetrahydropyran‐2‐yl)acetic acid and of (−)‐(R,R)‐Didesoxy‐pyrenophorine Using a New d5‐Reagent. Preliminary communication

The Li/K‐derivative6is used to synthesize the title compounds (3aand4a) in enantiomerically pure form from (−)‐(S)‐propylene epoxide. The C,C bond forming key step leading to the hydroxyketone 7 is followed by cyclization (→,8), Beckmann cleavage (→9b) and hydrolysis to3a(recently isolated from civet). Base treatment of3aopens the ring (10) to give the hydroxyacid1which is cyclized to the macrolide4a. The synthetic usefulness of the highly nucleophilic doubly reduced dienone system6as d5‐reagent (see synthons 2) is thus demonstirated.