73 多目的五炭素キラル素子の合成と天然物合成への活用(口頭発表の部)

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Starting from (S)-1,2-O-isopropylideneglycerol (5) as a sole chiral origin three five-carbon chiral building blocks 8, 10, and 11 were prepared efficiently in both enantiomeric forms via O-benzylglycidol (7). Namely, upon the reaction with acetylene in DMSO, 7 yielded the terminal acetylene-alcohol (8) in the presence of sodium hydride, while it afforded the internal acetylene-alcohol (9) with concomitant triple bond migration in the presence of potassium t. butcixide. The latter was further transformed into the (E)-allyl alcohol (10) by reduction with lithium aluminum hydride and the (Z)-ally1 alcohol (11) by reduction using Lindlar catalyst, respectively. The terminal acetylene (8), on sequential carboxylation and partial hydrogenation, afforded the α,β-unsaturated lactone (14) which furnished dehydrolavenderpyran (18) via stereoselective cuprate addition. On the Claisen-Johnson reaction only the (E)-alcohol (10) allowed diastereoselective rearrangement to give the homochiral ester (15) which was transformed to citronellal (19). On the other hand, on the Wittig rearrangement via the propargyl ether (13) only the (Z)-alcohol (11) allowed diastereoselective rearrangement to give the single acetylene-alcohol (16) which was transformed to elm bark beetle pheromone (21) and serricornine (23). Utilizing these building blocks jointly, we next attempted the synthesis of more complex polyketide maclorides, e. g., protomycinolide IV (1), milbemycin β_2 (2), amphotericin B (3), and mycoticin B (4). We have so far attained to protomycinolide IV (1) in formal sence, northern half (35) of milbemycin β_2 (2), C_<31>-C_<37> moiety (58) of amphotericin B (3), C_<27>-C_<34> moiety of mycoticin B (4), and key 1,3-glycol blocks, 50 and 51, of both 3 and 4.
天然有機化合物討論会の論文
1988-09-26

73 多目的五炭素キラル素子の合成と天然物合成への活用(口頭発表の部)

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