Synthesis of Chiral α,α-Difluoro-β-hydroxy Esters by Enantioselective Reformatsky Reaction

Towards 20,20-difluorinated bryostatin: synthesis and biological evaluation of C17,C27-fragments

The syntheses of compounds corresponding to 20,20-difluorinated C17–C27 fragments of bryostatin are reported together with preliminary PKC binding data.

Palladium-Catalyzed Enantioselective Ring Opening of Oxabicyclic Alkenes with Organozinc Halides

Palladium-catalyzed asymmetric ring opening of oxabenzonorbornadienes with readily available organozinc halides under mild conditions in the presence of (S)-Pr(i)-PHOX produces the corresponding 1,2-dihydronaphth-1-ols in good yield and high enantioselectivity. [reaction: see text]

Electroreductive Defluorination of Trifluoromethyl Ketones and Trifluoroacetic Acid Derivatives

Difluoroenol silyl ethers 5 and 6, difluoroketene silyl (O,O-, O,S-, and O,N-) acetals 9 and 21, and 2,2-difluoro-2-trimethylsilylacetates 10 were prepared by electroreductive defluorination of trifluoromethyl ketones and trifluoroacetic acid derivatives in an MeCN-TBAB-chlorotrialkylsilane system using a carbon rod as an anode and a lead plate as a cathode. TBAF- or KF-CuI-promoted alpha-alkylation of 10 with electrophiles such as aldehydes, ketones, imine, acylhalides, and alkylhalides provided alpha-alkylated-alpha,alpha-difluoroacetates in good to excellent yields.

Preparation of optically active trifluoromethylated (3′-indolyl) thiacarboxylic acids, novel plant growth regulators, through lipase-catalyzed enantioselective hydrolysis

Among a variety of lipases tested, that obtained from Candida antarctica (SP 435) induced enantioselective hydrolysis of trifluoroethyl 5,5,5-trifluoro-4-(3'-indolyl)-3-thiapentanoate (1c). The selectivity could be increased by optimizing the reaction conditions. Thus, good selectivity was achieved (E = 37) in a buffer containing 10% dichloroethane. In order to improve the optical yields, a sequential kinetic resolution was utilized for the preparative-scale enantioselective hydrolysis of 1c using SP 435. Hydrolysis of trifluoroethyl 6,6,6-trifluoro-5-(3'-indolyl)-4-thiahexanoate (2c) with the lipase of Pseudomonas aeruginosa (LIP) in a buffer containing 20% tert-amyl alcohol at 25 degrees C gave excellent selectivity (E=357).

Relationships between some soil parameters and the blood glutathione peroxidase activity of grazing sheep

The relationships between some soil parameters and blood glutathione peroxidase (GSHPx) activity in 15-day-old lambs was studied on 18 sheep farms. Soil samples were analysed for the proportions of sand, silt and clay, pH, and the concentrations of calcium, phosphorus, iron, nitrogen and sulphates. On the farms where the lambs had adequate GSHPx activity (> or = 130 i.u./g Hb) the soils contained significantly more clay, phosphorus and sulphates, and significantly less iron and nitrogen, than on the farms where the lambs did not have adequate GSHPx activity.