63 新規な1-hydroxyindole化合物群合成法の開拓とその天然物合成への応用(ポスター発表の部)

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I. A new and simple synthesis method for 1-hydroxyindole derivatives was developed based on the oxidation of indolines with either metal oxides and H_2O_2 or m-chloroperbenzoic acid (Table I and H). Thus, treatment of indolines 9a-f with Na_2WO_4・2H_2O and H_2O_2 in MeOH-H_2O afforded MeOH-H_2O solution A including quite unstable 1-hydroxyindoles 1a-f. Addition of ethereal diazomethane, dimethyl sulfate or alkyl halides to the solution A in the presence of K_2CO_3 produced 1-alkyloxy- and 1-allyloxyindoles (Table III). Addition of benzene and H_2O to the solution A and separation afforded benzene solution B including 1-hydroxyindoles. 1-Benzoyloxy- (1m) and 1-t-butyldi-methylsilyloxyindole (1n) were produced utilizing the solution B. II. We have succeeded in the development of the regioselective C-2 lithiation of indoles in the presence of readily removable group at the 1-position. Thus, 2a led to 14a-c in excellent yields (Chart 2) only by mixing with n-BuLi at ice-salt temperature, followed by trapping with electrophiles. Our present method would be useful for the synthesis of various indole alkaloids and 2-substituted indoles. III. i) Applying our method for 1-hydroxyindoles, 9-methoxy-3-in-dolecarboxaldehyde (30) was synthesized for the first time as shown in Chart 3. ii) The first total synthesis of methoxybrassinin (37) was achieved as shown in Chart 4. In the course of this work, we developed a new mild method for reduction of oximes into amines in the presence of unstable 1-methoxy group. We have also newly found that the syn- (32a) and anti-oxime (32b) can be isolated in crystals.
1990-09-25

63 新規な1-hydroxyindole化合物群合成法の開拓とその天然物合成への応用(ポスター発表の部)

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