Phenols, quinones, chromans, and chromens which have polyprenyl units as the side chains in aromatic compounds, are widely distributed in the natural products and many of these compounds are known as biologically active compounds. This review deals with recent advances in the syntheses of Vitamin E (α-tocopherol and α-tocotrienol), Ubiquinones (Coenzyme Q) and Vitamin K (K1 and K2).
New isocyanates, new synthetic methods of isocyanates, new reactions of isocyanates and industrial applications of isocyanates are reviewed, based on primary journals and Chemical Titles published in recent 10 years.
Maytansine, an extraordinary antitumor agent, was stereoselectively synthesized in 1980 by Corey group. The remarkable strategy, the new reagents and reactions of the total synthesis are explained in detail here. Also, the syntheses of maytansinoids by Meyers group are briefly mentioned.
Preparative methods (P), reactions (R), and synthetic applications (S) of quinone bisacetals (I) and monoacetals (II) are reviewed. P-I : (1) electrochemical methods (anodic oxidations) and (2) organochemical methods ; : (1) hydrolysis, (2) hydrogenations, (3) reactions with nucleophiles, and (4) reactions of lithio derivatives of I ; and S-I : (1) isoprenoid quinones and (2) anthracyclinones. P-II : (1) electrochemical methods, (2) organochemical oxidation of p-alkoxyphenols, (3) partial hydrolysis of quinone bisacetals, and (3) hydrolysis of the monoacetals of p-quinone monosulfonimides or nucleophilic reactions of o-quinone monosulfonimides ; R-II : (1) nucleophilic additions, (2) 1, 4-additions of carbanions, and (3) reductions ; and S-II : (1) bishomoquinone and triasteranetrione, (2) tropolones, (3) neolignans, (4) cherylline, (5) anthracyclinones, (6) gymnomitrol, (7) asatone, (8) ryanodol, and (9) α-tocopherol.
This article describes the asymmetric inductions in the intermolecular asymmetric Diels-Alder reactions. The reactions are classified into three groups : 1. Reactions of chiral dienophiles with dienes. 2. Reactions of chiral dienes with dienophiles. 3. Reactions catalyzed by chiral catalysts. The relationships between the absolute configuration of the chiral reagents and that of the products is discussed.
The currently available methods via allylic organometallic compounds for the stereoselective synthesis of homoallyl alcohols are summarized. Usually, Z-allylic organometallics give erythro adducts upon treatment with aldehydes, while E-derivatives afford threo products. Interestingly, allylic stannanes react with aldehydes in the presence of BF3·OEt2 to give erythro products regardless of the geometry of the double bond. A short and stereoselective synthesis of the Prelog-Djerassi lactone is realized via this method. The metal effect on the stereoselection of enolate reaction is also summarized. Zirconium and tin enolates give erythro aldols irrespective of the enolate geometry. α-Mercurioketones undergo a. rapid reaction with aldehydes in the presence of BF3·OEt2 to give the kinetic erythro aldols. These erythro selections are explained by the acyclic mechanism.
Agricultural chemicals industries in Japan have developed remarkably in recent years. Therefore the author thinks it necessary to write an up-to-date review concerning the agricultural chemicals industry. This review contains several items as follows : Feature of pesticide chemicals. Production amounts of pesticides. Import and exports of pesticides. Diminishing of toxic pesticides. Development of mixture of pesticides. Overseas affiliates of Japan pesticide companies. Present situation of pesticides industries. Major manufactures and their production of pesticides. Future aspects. New chemicals. Mutural relationship of companies. The author wrote this review with many useful tables written in English. In conclusion, safer and more effective pesticides in future should be developed as soon as possible to cope with worsening world-wide food crisis.
Both isomers of O-4-tert-butylcyclohexyl S-methyl dithiocarbon ates were synthesized in pure form from corresponding 4-tert-butylcyclohexanol via alkoxides. The cis alkoxide was prepared from cis alcohol and dimsyl sodium in DMSO, while the trans isomer was obtained by the equilibration of the alcohol mixture.