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A total synthesis of 6,7-dihydroeponemycin 2 was achieved via the epoxide intermediate 8a . Unresolved absolute configuration of the epoxide ring in 2 and eponemycin 1 was determined to be 2 R by application of the asymmetric Sharpless epoxidation of 9 .

The 2''-O-, 3''-O- and 2'',3''-di-O-substituted derivatives (4a--p) of etoposide were prepared by nucleophilic substitution of 4'-O-benzyloxycarbonyletoposide (2) followed by deprotection. Controlled reaction (a limited amount of reagents and low temperature) was required for preparing the mono-O-substituted derivatives. In terms of ED125 values, doses which show 125% of T/C against P388 leukemia in mice, both the 2''-O-acetate (4a, ED125 = 0.18 mg/kg) and 3''-O-acetate (4b, 0.23 mg/kg) were nearly as active as etoposide (1, 0.19 mg/kg), while the 2'',3''-di-O-acetate (4c, 1.9 mg/kg) was somewhat less potent. In the replacement with other substituents, antitumor activity of the 2''-O-substituted derivatives was affected much more by the difference of the substituents as compared with that of the corresponding 3''-O-substituted derivatives. In the 2'',3''-di-O-substituted derivatives, the activity was decreased additively on the substituents.

As part of a search for new potent derivatives, electrochemical oxidation of etoposide (1) was carried out under controlled potential (500 mV) to yield 1,2-dehydroetoposide (4), 4'-O-demethyl-1,2,3,4-tetradehydro-4-dehydroxy-podophyllotox in (5) and 1,2,3,4-tetradehydroetoposide (6). They showed no cytotoxicity against B16-melanoma.

Controlled crisscross annulation was applied to the synthesis of (±)-dihydrodesoxyotonecine, a degradation product of secopyrrolizidine alkaloids.

The synthesis of the nuclei of pyrrolizidine and indolizidine could be readily achieved by use of the one pot reaction named as “crisscross annulation”, which was extended to the synthesis of (±)-heliotridane ( 16 ) and (±)-nuphar indolizidine ( 20 ), a minor component of dried scent glands of the Canadian beaver.

Phoracantholide I, having a ten-membered lactone, was synthesized through a new synthetic method which includes a cyclic acetylenic oxy-Cope rearrangement and ring-expansion by the Baeyer-Villiger oxidation of a nine-membered ketone.

A synthesis of 9a-hydroxy-5,8-dideoxomitosanes was accomplished by the transannular cyclization of hydro-1-benzazocinone intermediates derived from 3-(2,5-dioxo-1-methylcyclopentyl)-6-methyl-p-phenylenediamine derivatives. These mitosanes were led to the 8-membered ring system by an oxidative ring-opening reaction.

(±)-Tryptoquivaline G was formally synthesized through shortened steps from tryptophan, in which oxidation with thallium(III) trinitrate(TTN) was effected at the crucial stage. The present work also constitutes the first synthesis of oxindole lactones carrying 2-alkyl quinazolinones.