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Ab initio MO calculations were performed on the cyclopropanation reaction of methylidenemalononitriles with the ylide generated from α-pyridiniumacetates. The calculations indicated that the rate-determining step was the final cyclopropane forming step for the gas phase reaction, whereas solvent effect approximations implied that it was the initial Michael addition leading to the cis intermediate for reaction in water. It was also revealed that the plausible [3+2] cycloaddition reaction to give bicyclic products is more likely to be a stepwise and not an asynchronous concerted process in DFT calculations at the B3LYP/6-31G(d) level of theory.

(2S,6S)-2,4,6-Tris(phenylmethyl)piperazine was prepared in 11 steps and 53% overall yield from S-phenylalanine. Key steps in the synthesis involved reductive amination to introduce an ethoxycarbonylmethyl group on to the secondary nitrogen of the product and selective alkylation to introduce a benzyl group with complete diastereoselectivity.

The reaction between β-substituted methylidenemalononitriles and the ylide from (-)-8-phenylmenthyl α-pyridiniumacetate, which affords activated cyclopropanes bearing two cyano groups and one carboxylic ester group, was examined. The trans isomer was obtained in up to 91:9 diastereoselectivity under optimized solvent conditions for the t-butyl substituted substrate. The selectivity increased to 96:4 upon using 4-methoxypyridine in the place of pyridine, whereas selectivities were generally lower for N,N-diethylnicotinamide. The major 4-pyridyl substituted cyclopropane was determined to be trans-1R by X-Ray structural analysis.

The Julia-Colonna asymmetric epoxidation reaction of substituted benzalacetophenone afforded the corresponding epoxide with high yield and high enantioselectivity, catalyzed by the specified length of poly-L-leucine (chain length n > 15). Poly-L-leucine catalysts have been prepared by the polymerization reaction of L-leucine-NCA with initiators (BnONa, n-BuNH 2 , H 2 O) and characterized by the MALDI-TOF Mass and IR analysis.

An analogue of the hydrophilic moiety of scyphostatin was synthesized via π-facial selective Diels-Alder reaction of a 2,5-cyclohexadien-1-one bearing a spirolactone with cyclopentadiene.

The Diels-Alder reactions of cross-conjugated ketones bearing an oxa-spiro-ring with some simple sterically undemanding dienes (cyclopentadiene, 2,3-cyclohexadiene, 2,3-dimethyl-1,3-butadiene) afforded the adduct with high π-facial selectivity under mild conditions. The π-facial selectivity can be explained in terms of Cieplak model.

The selective monochlorination of 5-[2-(N-silyl-amino)vinyl] isothia- zoles (1a,b) and their related compounds (1c,d, 2a-g, 3a-c, and 4a,b) with N-chlorosuccinimide is described. Chlorination of (1a,b) occurred at vinyl carbon to give (5a,b) and the geometry was determined to be Z-isomer according to spectral data. It is noteworthy that (1d) smoothly occurred bond switch at room temperature but (5)d did not ring-trans- form under the same conditions

Methylation of the title compounds (10-S-3 sulfurane: 1-3) took place exclusively on the nitrogen at 3(4)-position and selectively on the nitrogen bound to the more electron-withdrawing heterocycle. The acti- vation energy of the hindered rotation in 5 was lower for the pyrimidine ring (ΔGc = 20.2 kcal mol −1 ) bound to the methylated nitrogen than the other one (4Gc = 22.9 kcal mol −1 )

In the presence of 1,4-diazabicyclo[2.2.2]octane, 5-amino-3-methylisothiazole (4a) in acetonitrile condensed with N-methyl-p-chlorobenzimidoyl chloride (5a) to afford two kinds of compounds along with several minor products. One of the two was 1 : 1 condensed product (6a) and the other was 2 : 1 condensed product (7a). The latter compound was obtained in higher yield when an excess 4a was treated with 5a. On the other hand, in the absence of the additional base, 2 : 3 condensed compound (8a) was isolated as a major product besides 6a and 7a. 8a was obtained by treatment of 7a with 2 equiv. of imidoyl chloride in 21% yield. Reaction of 5-amino-3-phenylisothiazole (4b) with imidoyl chloride (5a,b) furnished the analogous products

A new simple methodology is described for the preparation of oxasteroidal skeletons containing a lactone ring via cycloaddition of 2-t-butyldimethylsiloxypyrylium triflate (2a,b) with syloxydienes.