Synthesis of (.+-.)-endo- and (.+-.)-exo-brevicomin via ene reaction of the Pummerer rearrangement product derived from 4-chlorophenyl methyl sulfoxide.

ISHIBASHI HIROYUKI, UEHARA CHIAKI, KOMATSU HAJIME, IKEDA MASAZUMI

doi:10.1248/cpb.35.2750

Synthesis of (.+-.)-endo- and (.+-.)-exo-brevicomin via ene reaction of the Pummerer rearrangement product derived from 4-chlorophenyl methyl sulfoxide.

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ISHIBASHI HIROYUKI

Kyoto Pharmaceutical University
UEHARA CHIAKI

Kyoto Pharmaceutical University
KOMATSU HAJIME

Kyoto Pharmaceutical University
IKEDA MASAZUMI

Kyoto Pharmaceutical University

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説明

(±) -endo- (4) and (±) -exo-Brevicomin (5) were synthesized by employing the ene-type reaction of 4-chlorophenylthiomethyl trifluoroacetate (2) as the key step. The ene product 7 was converted, via two steps, into the ketosulfone 9, whose epoxidation followed by acid hydrolysis afforded the cyclic acetal as a mixture, 12a and 12b (89 : 11). Recrystallization of the mixture followed by desulfurization yielded (±) -endo-brevicomin (4). On the other hand, successive treatment of 9 with osmium tetroxide, hydrochloric acid, and Raney nickel afforded a mixture of (±) -exo- (5) and (±) -endo-brevicomin (4) (89 : 11).