Preparation of alpha-aminobenzylphosphonic acids with a stereogenic quaternary carbon atom via microscopically configurationally stable alpha-aminobenzyllithiums.

The enantiomers of 1-phenylethylamine were phosphorylated with diethyl chlorophosphate/Et(3)N and then Boc-protected (Boc=tert-butoxycarbonyl) at the nitrogen atom. These phosphoramidates were metalated by using sBuLi/N,N,N',N'-tetramethylethylenediamine (TMEDA) to give alpha-aminobenzyllithiums that isomerised to alpha-aminophosphonates in yields of up to 80 % with retention of the configuration at the carbon atom. The intermediate tertiary organolithiums were found to be microscopically configurationally stable from -78 to 0 degrees C in Et(2)O.

Asymmetric construction of quaternary carbon stereocenters: high stereoselection in Mukaiyama aldol reactions of 2-siloxyindoles with chiral aldehydes.

[reaction: see text] A new synthesis of enantiopure 3,3-disubstituted oxindoles by stereoselective Mukaiyama aldol reaction of 3-substituted 2-siloxyindoles and chiral, enantiopure aldehydes having nitrogen or oxygen substituents at the alpha carbon is described. When the C3 substituent of the prochiral nucleophile is aryl or heteroaryl, stereoselectivity is high (10-80:1).

Total synthesis of the microtubule stabilizing antitumor agent laulimalide and some nonnatural analogues: the power of Sharpless' asymmetric epoxidation.

Three different routes are described for the synthesis of deoxylaulimalide (3), which is the immediate precursor of the marine sponge metabolite laulimalide (1). These routes mainly differ with respect to their ring closing step. Thus, route 1 uses a Still-Gennari olefination, route 2 a Yamaguchi lactonization, and route 3 an intramolecular allylsilane-aldehyde addition for establishing the macrocyclic structure.