Yoshiki Morimoto

An efficient approach toward pyrrolidinyllactone system characteristic of the Stemona alkaloids. Lewis acid catalyzed stereoselective reaction of N-benzyloxycarbonyl-2-methoxypyrrolidine with 3-methyl-2-trimethylsilyloxyfuran

Abstract Pyrrolidinyllactone system 7 , common partial structure presented in most Stemona alkaloids, was stereoselectively prepared by two-step sequence: i) syn -selective condensation of N -benzyloxycarbonyl-2-methoxypyrrolidine ( 8 ) with 3-methyl-2-trimethylsilyloxyfuran ( 9 ) catalyzed by Lewis acids; ii) diastereoselective hydrogenation of the product 10 (NaBH 4 , NiCl 2 / MeOH).

Stereocontrolled Total Synthesis of the Stemona Alkaloid (−)-Stenine

The Stemona alkaloid stenine (1), isolated from Stemona tuberosa of physiologically active stemonaceous plants, possesses the structurally novel and unique azepinoindole skeleton (B,C,D-ring system). We have achieved the asymmetric total synthesis of (-)-stenine (1), starting from 1,5-pentanediol (10). The key features are an intramolecular diastereoselective Diels-Alder reaction of the (E,E,E) triene 6, prepared in a convergent fashion from three components--dienyl chloride 7, dithiane 8, and chiral phosphonate 9--and efficient construction of the tricyclic A,B,D-ring system 29 through thermodynamically controlled regioselective enolization of the bicyclic ketone 25. In this article, we describe in detail the highly stereocontrolled total synthesis of (-)-stenine (1). These results should be useful for the asymmetric total synthesis of another, more complex. molecule: tuberostemonine (2), the synthesis of which has never been reported.

Synthetic studies on virantmycin. 1. Total synthesis of (±)-virantmycin and determination of its relative stereochemistry

Abstract The efficient and stereospecific route to the tetrahydroquinoline ring models 3 and 4 of virantmycin has been developed by means of an intramolecular nitrene addition reaction as a key step. In the NOE experiments of 4 and 3 we revealed that a ring inversion occurs in their piperidine ring system and determined the relative stereochemistry by capturing each half-chair conformer as cyclic carbamates 26 and 27 , respectively. Utilizing this protocol total syntheses of (±)- 1 and its diastereomer (±)- 2 have been accomplished and the relative stereochemistry of virantmycin has been established as shown in 1 .

Total Synthesis and Determination of the Absolute Configuration of (+)‐Omaezakianol

The proof of the pudding: The first asymmetric total synthesis of the marine tetracyclic oxasqualenoid (+)-omaezakianol features a convergent olefin cross-metathesis between a monotetrahydrofuran fragment and a triepoxy alkene, and cascade oxacyclizations of a triepoxy alcohol to form the right-hand three ether rings. The total synthesis proved the absolute configuration of (+)-omaezakianol to be that shown.

Limonoids from the stem bark of Cedrela odorata

Four nomilin/obacunol derivatives and a swietenolide derivative, together with seven known limonoids, were isolated from stem bark of Cedrela odorata and their structures established by spectroscopic methods. Antifeedant activity of the isolated compounds was also tested.

Diastereoselective two-directional synthesis and cation transport ability of the central tristetrahydrofuranyl unit of meso polyether glabrescol as naturally occurring podand

The diastereoselective synthesis of the central 2,5-linked tristetrahydrofuran (trisTHF) 6 of naturally occurring meso polyether, glabrescol (5), has been achieved in a two-directional manner by the vanadium(V)-catalyzed anti oxidative cyclizations of diol 14. The trisTHF podand 6 and its stereoisomeric analogs 7 and 8 exhibited outstanding cation transport abilities for physiologically important Na+ and K+.

Synthetic studies on virantmycin. 2. Total synthesis of unnatural (+)-virantmycin and determination of its absolute stereochemistry

Abstract The enantioselective total synthesis of (+)-virantmycin ( 1 ) has been achieved by means of the Sharpless asymmetric epoxidation of allylic alcohol 27 followed by an intramolecular epoxide opening of the exo epoxy alcohol 32 which was derived from the endo epoxy alcohol 28 . The synthesis of (+)- 1 has established that the absolute configuration of the natural product (−)- 1 is shown to be 2 R , 3 R at the two chiral centers. Further, antiviral activities of the virantmycin analogs were also examined against influenza virus.

Aplysinopsin dimers from a stony coral: Tubastraea aurea

- Five novel bis(indole) alkaloids, which were composed of two molecules of aplysinopsin have been isolated from a stony coral, Tubastraea aurea. Their structures were elucidated on the basis of spectroscopic methods.

Total synthesis and determination of the absolute configuration of (−)-longilene peroxide

Abstract The first asymmetric total synthesis of (−)-longilene peroxide ( 1 ) has been achieved starting from the optically active C 2 -symmetric diepoxide 5 through the concept of two-directional synthesis utilizing its intrinsic molecular symmetry. Thus, the unknown absolute configuration of longilene peroxide has been determined by this synthesis as shown in the structural formula 1 .

Total syntheses of macrocyclic marine alkaloids, haliclamines A and B: A convenient and expeditious assembly of 3-substituted pyridine derivatives with different alkyl chains to the bispyridinium macrocycle

Abstract The total syntheses of haliclamines A (1) and B (2), macrocyclic marine alkaloids closely related to the key bisdihydropyridine intermediate 3 of the biogenetically unique manzamine family, have efficiently been achieved via stepwise controlled inter- and intramolecular N-alkylations of 3-alkylpyridine derivatives such as 40 and 41. The general synthetic methodology toward the bispyridinium macrocycle 44, a key biogenetic equivalent of the polycyclic marine alkaloids, has been proposed through the total syntheses.