Journal of the Chemical Society. Perkin transactions I p. 1191 - 1196 (1981)
Update date:2022-09-26
Topics: Retrosynthetic analysis Final steps Construction of the Core Structure Assembly of Fragments
Kometani, Tadashi
Yoshii, Eiichi
The syntheses of 9-demethoxyeleutherins and 9-deoxynanaomycin A methyl ester starting from indan-1-one derivatives are described.Lemieux-Johnson oxidation of the indene (15) derived from 4,7-dimethoxy-2-methylindan-1-one (14) afforded the diketone (16).The diol (17) obtained by lithium aluminium hydride reduction of (16) was treated with hydrochloric acid to give a ca. 1:2 mixture of cis-5,8-dimethoxy-1,3-dimethylisochroman (18) and the trans-isomer (19).Treatment of (16) with hydrogen bromide in acetic acid followed by catalytic reduction gave exclusively the cis-isochroman (18).Oxidative demethylation of the isochromans (18) and (19) afforded the quinones (22) and (23), benzannelation of which in two steps yielded 9-demethoxyeleutherin (24) and 9-demethoxyisoeleutherin (25) respectively.The same oxidation of the indene (32) derived from 4,7-dimethoxyindan-1-one (28) afforded the keto-aldehyde (33), which was treated with methoxycarbonylmethylenetriphenylphosphorane to give the conjugated ester (34).Reductive cyclisation of (34) with sodium borohydride afforded a ca. 1:3.5 mixture of cis-5,8-dimethoxy-3-methoxycarbonylmethyl-1-methylisochroman (35) and the trans-isomer (36).Oxidative demethylation of (36) followed by benzannelation produced 9-deoxynanaomycin A methyl ester (39).
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(1981)
