Nitrosation of various α, β-unsaturated carbonyl compounds with nitrogen monoxide or butyl nitrite was achieved in the presence of silane and a catalytic amount of N, N' -bis (2-ethoxycarbonyl-3- oxobutylidene) ethylenediaminatocobalt (II) complex catalyst. In the presence of a catalytic amount of tris (1, 3-diketonato) iron (III) complex, various terminal and 1, 2-disubstituted olefins were converted into the corresponding nitroso alkane dimers in fairly good yields on treatment with phenylsilane and butyl nitrite. Nitration of various terminal olefins into corresponding nitro olefins were performed on treatment with nitrogen monoxide. Nitroalcohols, minor coproducts, were dehydrated to yield nitro olefins by the subsequent treatment with acidic activated aluminum. By GC analysis, evolution of an equimolar amount of nitrogen gas was observed during the present nitration. A possible reaction pathway including the formation of nitro nitroso compounds, key intermediates, was proposed.
A total synthesis of the microbial metabolite (+) -lactacystin (1), the first non-protein neurotrophic agent, has been achieved in 11 steps (14% overall yield) from 2 (R), 3 (S) -3-hydroxyleucine. The key steps in the elaboration of the lactam moiety include the stereoselective hydroxymethylation of oxazoline and an asymmetric allylboration of the aldehyde which introduce the hydroxyl and methyl substituents at C (6) and C (7). This new asymmetric approach furnished four stereoisomers of 3-hydroxyleucine as required starting material in high overall yield and enantiomeric purity. Furthermore, the construction of several active analogs and the structure-activity relationships of lactacystin are also described.
The developments of novel electron donors of non-TTF types are described, especially focussing on peri-condensed heteroarenes bearing a structural resemblance to pyrene or perylene and on peri-dichalcogen bridged arenes like tetrathiotetracene. These compounds have been designed chiefly to provide strong donating abilities and strong intermolecular heteroatomic contacts, which are prerequisites for components of organic metals. As a result, some of them have stronger donating abilities than does tetrathiafulvalene (TTF), thus providing a large number of highly conducting molecular complexes.
Our recent studies on synthesis, stereochemical analysis, and tropicity of various dehydroannulenes, annulenones, annulenediones, cross-conjugated annulene derivatives, and heteraannulenes are reviewed. Our efforts consist mainly of the design and construction of novel peripherally conjugated systems and the exploration of the highest member in each series of compounds exhibiting tropicity.
In order to stabilize triplet carbenes kinetically to extent that they are able to survive under normal conditions, attemps were made to protect the carbenic center of triplet diphenylcarbenes by introducing a series of substituents at the ortho position. Thus, diphenylcarbenes bearing chloro, methyl, t-butyl and bromo groups at the ortho positions were generated by photolysis of the corresponding diazo compounds and were characterized not only by product analysis but also by direct observation using spectroscopic means. Thus, decachloro- and decamethyldiphenylcarbenes were shown to be four and five orders of magnitude longer-lived than the parent diphenylcarbene, respectively. The replacement of all the o-CH3 groups of decamethyldiphenylcarbene with CD3 groups greatly decreased the intramolecular H abstraction rate from the o-methyl groups and resulted in the formation of triplet carbene having half-life over second in solution at room temperature for the first time. On the other hand, t-butyl group was shown to be disappointingly less effective protector of the triplet carbene due to its ability of H transfer to the carbenic center. 2, 2', 4, 4', 6, 6'-Hexabromodiphenylcarbene was found to be very persistent in the triplet states. Thus, EPR signals of the carbene generated in single crystals of the diazomethane survived up to room temperature without loss of intensity for months. In 2-methyltetrahydrofuran matrix the carbene showed no decomposition even at 120 K where the samples were completely fluid. Replacement of bromine groups at 6 and 6' positions of the hexabromodiphenylcarbene with t-butyl groups resulted in increase in the lifetime of the triplet carbene under normal conditions to ca 20 seconds which is 108 times longer lived than the parent diphenylcarbene.
A series of isoquinolinesulfonamide derivatives were synthesized and shown to possess vasodilatory action. 1- (5-Isoquinolinesulfonyl) homopiperazine hydrochloride (fasudil) had more potent vasodilatory effect to vertebral artery than diltiazem. Fasudil inhibits protein kinase and dilates spastic cerebral arteries in the canine two-hemorrhage model. In clinical studies with fasudil administered by intravenous injection in patients who had undergone sugery for subarachnoid hemorrhage, fasudil significantly reduced the occurrence of vasospasm. In Japan, fasudil was approved in june, 1995.