Synthetic works on the Amaryllidaceae alkaloid, lycorine, were critically reviewed with 30 references including the following articles : syntheses of lycorine skeleton, four stereoisomers of lycorane, substituted lycoranes, and author's work on the total synthesis of lycorine. The highlight was the last article which started from Diels-Alder reaction of 3, 4-methylenedioxyphenylbutadiene and fumaric acid followed by construction of four rings of lycorine in the order of A→C→B→D, during which work a new procedure of Bischler-Napieralski cyclization of β-phenylethylurethans for construction of ring B was presented and its potential utility for the synthetic chemistry was demonstrated. The key-intermediate (1-dehydrolycorane-lactam) thus synthesized was transformed divergently in stereoselective manners to the natural alkaloids, α-dihydrolycorine, zephyranthine, and finally to lycorine.
This review article deals with various aspects of organosilicon compounds which were used in organic synthesis with some emphasis of the latest advances in the area that they concern. After a primer of the organosilicon chemistry, the topics are discussed in the following six items : (i) silyl enol ethers ; (ii) alkenyl- and alkynyl-silanes ; (iii) condensation of Peterson type ; (iv) silicon pseudohalides ; (v) hydrosilane reductions ; (vi) miscellaneous reactions.
The reactions of various β-hydroxy esters with vinylmagnesium chloride was described. Divinyl tertiary carbinols were obtained from the reaction of α-nonsubstituted β-hydroxy esters with vinylmagnesium chloride, while β-hydroxy ketones containing terminal vinyl group were obtained from the reaction of α-substituted β-hydroxy esters with vinylmagnesium chloride.
Cis- and trans-3-benzylamino-1- (2-ethoxyethyl) -1, 2-dimethyl-7-methoxytetraline obtained from tyrosine according to the previous method were converted to cis- and trans-pentazocine, respectively, by debenzylation, N-alkenylation, and finally cyclization
Factors influencing the asymmetric selectivity in the hydrogenation of methyl acetoacetate to methyl 3-hydroxybutyrate by the nickel-palladium-kieselguhr catalyst were studied in order to improve the optical purity of the product. Optimum pH-value of the tartaric acid solution for modification of the catalyst was found to be 4.34.5. A slight increase of the asymmetric yield was attained by preheating the catalysts in the solvent and/or by preheating the reaction mixtures under hydrogen pressure without stirring. Thus, the product having [α] 20D-20.10° (optical purity 91.2%) was obtained in the best condition.