Keishi Kotera

Structure of securinine

Abstract The structure (XXVII) proposed for securinine is confirmed by synthetic structural proof of the key degradation products, lactam-carbinol B (XXIII) and quinolizidine B (XX).

Application of the remote photocyclization with a pair system of phthalimide and methylthio groups: A photochemical synthesis of macrolide models

Abstract Based on the regioselective remote photocyclization of a pair system consisting of a phthalimide group and a terminal sulfide group in their side chain, a variety of azathiacyclic compounds containing 9- to 27-membered rings were synthesized.

Reaction of 3-phenylglycidic esters. Part 2. Stereo- and regio-selectivity in the oxirane ring opening of methyl trans-3-(4-methoxyphenyl)glycidate with various thiophenols and the effects of solvent and temperature

The effects of the solvent and temperature on the reaction of the trans-glycidate (1) with various substituted thiophenols (2) in the presence or absence of a catalyst have been investigated. The temperature had a surprisingly large effect on the stereochemistry of the oxirane ring-opening of (1). At room temperature, the erythro-isomer (4)(trans-opening product) was obtained as a major product in the absence of catalyst, while the cis-opening product (3)(threo-isomer) was produced predominantly at higher temperature. On the other hand, in a dipolar aprotic solvent, the regioisomer (5) was formed, the yield increasing with the electron-donating ability of the substituents on (2). The formation of compound (5) may involve single-electron transfer as a key step.

Hydrogenation of cyclobutanes in strained cage compounds. Synthesis of ditwistane and bisnorditwistane (ditwistbrendane)

The central bond of the bicyclo[2.2.0]hexane system of the dimeric cage compound synthesized photochemically from N-chloroacetyltyramine was hydrogenated with 10% Pd–C to give the dihydro-compound. Similarly 7,10-dihydroxy-1,4,7,10-tetramethylpentacyclo[6.4.0.02,5.03,12.04,9]dodecane-6,11-dione gave 6,12-dihydroxy-2,6,9,12-tetramethyltetracyclo[6.2.2.02,7.04,9]dodecane-5,11-dione, and its spectral data revealed the correct structure, which was confirmed by the X-ray analysis. This hydrogenation was extended to the synthesis of [8]-ditwistane and bisnorditwistane (ditwistbrendane). Thus, pentacyclo[6.4.0.0.2,503,12.04,9]dodecane-6,11-dione synthesized from salicyl alcohol was hydrogenated to give ditwistanedione. Dithioketalization and desulphurization gave ditwistane. All the rings of this compound are six-membered and in the distorted twist-boat conformation. Similarly, hydrogenation of pentacyclo[5.3.0.02,5.03,10.04,8]decane and its 6-one gave bisnorditwistane.

SYNTHETIC STUDIES ON 2-PYRROLIDINONE DERIVATIVES. II. THE CONFIGURATION OF STEREOISOMERS OF 1-PHENYL-3-AMINO-5-METHYL-2-PYRROLIDINONE.

The reductions of 1-phenyl-3-hydroxyimino-5-methyl-2-pyrrolidinone, using i) Platinum dioxide in glacial acetic acid, ii) Raney nickel in Ethanol, and iii) Aluminum mercury in moist tetrahydrofuran, were carried out to furnish two isomeric amines, designated as IIa and 1-phenyl-3-amino-5-methyl-2-pyrrolidinone (IIb). Quantitative ratios of these amines formed as regard to the reduction methods allowed us to assign cis-configuration to IIb and trans-configuration to IIa. From the studies of ultraviolet and nuclear magnetic resonance spectra of the 3-hydroxy-compounds, 1-phenyl-3-hydroxy-5-methyl-2-pyrrolidinone (IIIa) and 1-phenyl-3-hydroxy-5-methyl-2-pyrrolidinone (IIIb), prepared from IIa and IIb respectively, the occurrence of Walden-inversion in the diazotization reaction was concluded. At the same time cis-configuration of IIb and IIIa was also predicted, which was supported by leading IIIa to cis-1-tosyl-2-methyl-4-methoxypyrrolidine (X) synthesized from dl-allo-hydroxyproline.