145513-97-9

a- a- a- (1R,2S,5R)-Menthyldiphenylgermane and its enantiomer have been prepared in a few steps from germanium tetrachloride. The initial step in this sequence, namely the reaction between germanium tetrachloride and menthylmagnesium chloride, produces menthylgermanium trichloride, which is the exclusive product of this Grignard reaction, presumably due to the bulk of the menthyl group. When used at a low temperature (-78°C) and in conjunction with Lewis acids, such as magnesium salts, these chiral germanes are capable of reducing ester functionalized radicals in high enantioselectivity, but in low-moderate yield. For example, (R)-naproxen ethyl ester was obtained in 15% yield and 99% ee by reaction in toluene of 2-bromonaproxen ethyl ester with (1R,2S,5R)-menthyldiphenylgermane in toluene at -78°C in the presence of magnesium bromide. At 80°C, (1R,2S,5R)-menthyldiphenylgermane reacted with primary alkyl radicals with a rate constant of 1.02×106 M-1 s-1. Kinetic studies reveal the Arrhenius expression for this reaction to be: log(k/M-1 s-1) = (11.1 ± 0.4) - (34.6±3.1)/θ where θ=2.3RT kJ mol-1.

Although imines are convenient substrates for the synthesis of functionalized amines, they may be hard to obtain, as in the case of fluorinated imines. To aid in overcoming this issue, we propose a protocol of corresponding amine synthesis from simple fluoroacetic acid-derived amides using Schwartz's reagent.

The invention relates to new pteridines which are suitable for the treatment of respiratory or gastrointestinal complaints or diseases, inflammatory diseases of the joints, skin or eyes, diseases of the peripheral or central nervous system or cancers, as

The invention provides a method for enantioselectively reducing a prochiral carbon centred radical having one or more electron donor groups attached directly to the central prochiral carbon atom of the radical, and/or attached to a carbon atom within 1 to 4 atoms of the central prochiral carbon atom, comprising treating said radical with an activated chiral non-racemic organosilicon hydride in the presence of a Lewis acid. The invention also provides a novel class of activated chiral non-racemic organosilicon hydrides.

The invention provides a method for enantioselectively reducing a prochiral carbon centred radical having one or more electron donor groups attached directly to the central prochiral carbon atom of the radical, and/or attached to a carbon atom within 1 to 4 atoms of the central prochiral carbon atom, comprising treating said radical with a chiral non-racemic organogermanium hydride in the presence of a Lewis acid. The invention also provides a novel class of chiral non-racemic organogermanium hydrides and a method of preparing chiral non-racemic organogermanium compounds.

The new chiral bis(oxazoline) ligand 8 has been synthesized from (S)-phenylglycine and has been shown to form effective catalysts for enantioselective Diels-Alder addition in combination with ferric iodide, magnesium iodide or magnesium tetraphenylborate.Catalytic activation of the dienophile, 3-acryloyl-1,3-oxazolidine-2-one (4), in the magnesium system is proposed to involve tetrahedrally coordinated magnesium in a dispositive complex (10).