Simple and effective synthetic methods of polycylic ring systems in intramolecular reactions are presented. The first example is Diels-Alder reaction, which has been applied to total synthesis of steroids and terpenes. The intramolecular double Michael reaction is the second case, whose mechanism and application to natural product synthesis are also discussed. In addition, some related reactions of the latter are described.
Pyrazosulfuron-ethyl (1) is a new rice herbicide discovered and commercialized by Nissan Chemical Ind., Ltd. Research and development were started by introduction of heterocyclic moieties into an existing sulfonylurea herbicide as a lead compound which showed excellent herbicidal activities. Extensive investigations suggested a potent herbicidal activity in pyrazole rings as the heterocyclic moiety which led to the discovery of pyrazosulfuron-ethyl. Development of new synthetic methods for intermediate pyrazolesulfonamides with various functional groups made it possible to investigate pyrazolesulfonylureas (Fig.3). Various new 3, 4 and 5-pyrazolesulfonamides were synthesized to obtain the pyrazolesulfonylureas including pyrazosulfuron-ethyl. Six synthetic methods for the important intermediate pyrazolesulfonamide 14 were also developed for manufucturing pyrazosulfuron-ethyl. In this paper these synthetic methods and a final step to pyrazosulfuron-ethyl are described.
This article summarizes our several years-effort to realize cell adhesion control via biospecific ligandreceptor interaction for enhanced adhesion and physico-chemical surface design for non-cell adhesion. The minimal cell adhesive tripeptidyl sequence of Arg-Gly-Asp (RGD), common to adhesive proteins, was immobilized to polymer surfaces or derivatized to water-soluble and -insoluble polymers, resulting in the molecular architecture of 2-dimensional and 3-dimensional artificial extracellular matrix where cell adhesion and growth were attained. Photochemical surface fixation of cell-adhesive RGD-containing peptide and adhesive proteins or nonionic, hydrophilic polymers, all of which were derivatized with photoreactive groups such as azidophenyl, were successfully attained in the microns-order regional precision. This eventually leads to provide solid bases of biocompatible surface designs for fabricated cardiovascular devices and functional surface designs for microsensors and micromachines.
The synthesis of chiral compounds having fluorine atoms has become an important part of organofluorine chemistry in connection with analytical, biological and medicinal chemistry and opto-electric substances such as liquid crystals. This review is focused on asymmetric synthesis of chiral compounds having a fluorine atom or a fluoroalkyl group (especially a trifluoromethyl group). The examples cited in this review are divided in three different types; (a) asymmetric monofluorination, (b) asymmetric fluoroalkylation (trifluoromethylation), and (c) conversion from prochiral fluorinated compounds.
Enzymes have now been generally accepted as chiral catalysts in organic synthesis. Especially attractive in this regard are hydrolytic enzymes such as lipases and esterases, because these enzymes possess broad substrate specificity and can also function in nonaqueous media for certain types of transformation. Furthermore, hydrolytic enzymes do not require expensive coenzymes and are available commercially at low cost. In order for an enzyme to be applied widely as a chiral catalyst in organic synthesis, it is desirable that the factors controlling its stereospecificity be understood and rationalised. Recently, some active-site model for interpreting and predicting the stereoselectivity of hydrolytic enzyme-catalyzed reactions has been reported. This review will describe stereoselectivity of hydrolyses and acylations catalyzed by hydrolytic enzymes such as PLE, PPL, CRL, PFL, and PCL, and discuss application of active-site models in analyzing stereoselectivity of these reactions.
This review describes efficient means of preparing optically pure compounds via bakers' yeast mediated reaction or lipase-catalyzed reaction : (1) Bakers' yeast mediated reaction of cyanoketone was demonstrated and was discovered a new type of C-C bond forming reaction. (2) Hydrolysis of 2-substituted-3-acetoxy esters by Aspergillus lipase (lipase A 6) was demonstrated. According to summarize the stereo favoritism between substrates, the active site model of an Aspergillus lipase is proposed. (3) A simple preparation of optically active α- or γ-hydroxystannanes using Pseudomonas lipase (lipase PS) was realized. (4) Two effective means were discovered for enantioselective reaction of lipase PS : one is the modification of the acyl group by a sulfur functional group and the other is addition of a catalytic amount of l-methioninol or crown ether derivatives to the reaction mixture. (5) Optically pure (R) -4-hydroxy-3- (3, 4-methylenedioxyphenyl) methylbutanenitrile, obtained by this reaction, was applied to the synthesis of three anti-tumor lignans. (6) As a new chiral building block for tertiary alcohols, (R) -2-ally1-2- (phenylthio) methyloxirane was synthesized via lipase-catalyzed reaction.