103(P-22) 新光延試薬を用いた炭素-炭素結合形成反応 : フェロモン類の不斉合成への利用(ポスター発表の部)
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The Mitsunobu reaction, a popular alkylation reaction utilizing the redox system between diethyl azodicarboxylate (DEAD) and triphenylphosphine, has a shortcoming that it can only be applied satisfactorily to a nucleophile (HA) of pK_a less than 11. In order to overcome the limitation, we have recently introduced several combinations of azodicarboxamides, such as TMAD, DHTD, and tributylphosphine. In our continual search for new versatile reagents, we found cyanomethylene-tributylphosphorane (CMBP) and -trimethylphosphorane (CMMP) was capable of mediating the alkylation of various HA of larger pK_a than 11. These reagents, especially CMMP, mediate fficiently the alkylation of much weaker C-nucleophiles, such as cyanometyl phenyl sulfone 1 (pK_a=12.0 in DMSO), MT sulfone 2 (pK_a=23.4 in DMSO), arylmethyl phenyl sulfones 3 (pK_a=16.0〜23.4 in DMSO), prenyl phenyl sulfone (4b) (pK_a=〜22 in DMSO), and geranyl phenyl sulfone (4c). Most of the reaction with CMMP at 80-120℃ proceeded quite satisfactory with Walden inversion of carbinyl carbon on secondary alcohols. Two pheromone analogs were synthesized starting with the products 6 and 9 obtained by the reaction of (2S)-2-octanol with 1 and 2, respectively. Thus, the reductive elimination of the phenylsulfonyl group of 6, followed by the reduction of the resultant nitrile in two steps yielded (3R)-3-methylnonan-1-ol (7) which had been converted by Ozaki et al. to 8, analog of an aggregation pheromone of red flour beetles. The Sulfone 9 was also converted to (2R)-2-methyloctanol (10), which has been used by Hogberg et al. in the synthesis of the saw fly sex pheromone analog. Furthermore, norfaranal, an analog of the unique trail pheromone produced by Paraoh's ant, was synthesized in short-steps utilizing the reaction of geranyl phenyl sulfone (4c). Thus, we have demonstrated that C-nucleophiles of pK_a up to 23.4 can be utilized in the CMMP mediated Mitsunobu reaction. The C-C bond formation reaction, being much more versatile than ever, should find much wider application in organic syntheses.
- 天然有機化合物討論会の論文
- 2000-10-01
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