New bis- and tris-annulation reagents for the syntheses of CD rings of steroids,bearing a functionalized 18-methyl group,by the palladium-catalyzed cyclization

2-Substituted 2-alkoxycarbonyl-3-vinylcyclopentanones (2), easily prepared by the palladium-catalyzed cyclization of 2-substituted 3-oxo-8-phenoxy-6-octenoates (1), are very suitable building blocks for CD rings of steroids, bearing particularly a functionalized 18-methyl group.     

Efficient synthesis of alpha-C-galactosyl ceramide immunostimulants: use of ethylene-promoted olefin cross-metathesis

[reaction: see text] Olefin cross-metathesis has been used to prepare alpha-C-galactosylceramide derivatives. The metathesis process merged vinyl and propenyl glycosides with vinyl derivatives of phytosphingosine. The use of ethylene enhanced the yield of the methathesis step.     

On attempts at generation of carboranyl carbocation

We have synthesized all three possible isomers of C-hydroxycarborane from the corresponding amines via diazotization. The O-protonated C-hydroxycarboranes were characterized using the NMR spectrum measurements. Attempts at generating of carboranyl carbocations were carried out by the solvolyses of C-tosylates and C-triflates, as well as by treatment with superacids. Anchimeric assistance of both homoconjugative and hyperconjugative substituents was also investigated, as demonstrated by a successful strategy devised for the solvolytic generation of a phenyl cation. However, we have not been able to chemically provide any evidence of carboranyl carbocations, although the carboranyl carbocation may be an intermediate in the decomposition of the C-carboranediazonium ion.     

Four guaianolides from Sinodielsia yunnanensis

Four new guaianolides, sinodielides A-D (1-4), were isolated from Sinodielsia yunnanensis WOLFF together with a known polyacetylene, falcarindiol, and two known coumarins, bergapten and scopoletin. Their structures were established by spectral and X-ray analyses.     

Sigmasigma* transition in anti,cisoid alternating oligosilanes: clear-cut evidence for suppression of conjugation effect by a cisoid turn

On the basis of the UV absorption spectra of the anti,cisoid alternating oligosilanes, the first experimental clear-cut evidence was presented for the generally accepted idea that the sigma conjugation in polysilanes does not effectively extend through a tetrasilane fragment with a small dihedral angle such as a cisoid turn.     

Efficient synthesis of 2,4-disubstituted 1,2,4-benzothiadiazin-3-one 1,1-dioxides on solid support

The first solid-phase synthesis of 1,2,4-benzothiadiazin-3-one 1,1-dioxides has been developed. Synthesis of the title compounds was achieved by the reduction of 2-nitrobenzenesulfonamides, followed by cyclization with carbonyldiimidazole. Because 1,2,4-benzothiadiazin-3-one 1,1-dioxides have been known to possess various bioactivities, this method is useful from the viewpoint of new drug discovery. In addition to the excellent purity of the title compounds, a large number of compounds can be synthesized with this method, because this synthesis includes four diversity points.     

On the Iwasawa -invariants of real abelian fields

For a prime number and a number field , let denote the projective limit of the -parts of the ideal class groups of the intermediate fields of the cyclotomic -extension over . It is conjectured that is finite if is totally real. When is an odd prime and is a real abelian field, we give a criterion for the conjecture, which is a generalization of results of Ichimura and Sumida. Furthermore, in a special case where divides the degree of , we also obtain a rather simple criterion.