P-8 プロリン触媒不斉アルドール反応を基軸とする天然物の不斉全合成(ポスター発表の部)

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Recent advances in the field of organocatalytic asymmetric synthesis have provided several new methods for obtaining chiral compounds in an environmentally benign manner. Most attention has been focused on the use of proline due to its ready availability in either L- or D-form and the highly versatile nature of its reactivity. In particular, proline-catalyzed asymmetric aldol reactions have been extensively studied from the viewpoint of their synthetic value as well as mechanistic considerations. However, there is still a significant limitation on the use of unsubstituted aliphatic aldehydes as an aldol component. To solve this problem, we examined the use of several aliphatic aldehyde synthons 4〜6, and we found that the aldehyde 6 bearing a dithiane functionality at the β-position could serve as an efficient substrate. This method was successfully applied to the enantioselective synthesis of biologically interesting natural products including: 1. (-)-(5R,6S)-6-Acetoxy-5-hexadecanolide (1), an oviposition attractant pheromone of the female Culex mosquito. 2. D-ribo-C_<18>-Phytosphingosine (2), a class of long chain amino alcohol derivatives having an important role in cell regulation and signal transduction. 3. (+)-Boronolide (3), an α,β-unsaturated a C-12 lactone isolated from the leaves and branches of Tetradenia_fruficosa. Starting from the proline-catalyzed asymmetric aldol reaction, compound 1 was prepared in 35.6% overall yield via a 4-step sequence; compound 2 was prepared in 13.3% overall yield via a 10-step sequence. The important precursor 34 for the synthesis of 3 was also constructed in a good overall yield and in high enantioselectivity.
天然有機化合物討論会の論文
2005-09-15

P-8 プロリン触媒不斉アルドール反応を基軸とする天然物の不斉全合成(ポスター発表の部)

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