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The lithiated bis(1actim) ether 8a furnishes with aldehydes and ketones in good yields the addition products 11 with (3R) configuration. The asymmetric inductions at C-3 of 11 (d.e. values) amount to more than 95% with ketones, with aldehydes they are somewhat smaller. With unsymmetrical ketones or aldehydes C-3' also becomes a chiral center. For the (3R)-major diastereomers the "second induction" at C-3' varies from about 4 to about 87% (for benzaldehyde or isobutyraldehyde, respectively), preferably the (3R,3'S) epimers are formed. - Acid hydrolysis of 11 yields (besides methyl L-valinate) the (2R)-serine methyl esters 26. Their e.e. values correspond with the d.e. values of 11. - Dehydratation of 11 furnishes the "Hofmann olefins" 32 and/or the "Saytzeff olefins" 33 which can be transformed in various ways into optically active amino acids.

Enantioselective syntheses of α-alkenyl glycines of type 10 and of type 23 are described that provide these uncommon ammo acids with predictable conf&uration and with ec-values of >95%. Both approaches are based on the bislactim ether method developed by SchBllkopf et al. As for 10: The lithiated his-lactim ether 6 of cyclo(t-val-gly) is reacted with 2-[(dimethyl t-butyl)silyl]alkanals 2 to give the addition products 7 with de> 95%. These on acid hydrolysis afford L-valinate 8 and the methyl (2R)-2-amino4(dimethyl t-butyl)silyl-3-hydroxyalkanoates 9 which are convertible into the (R)-α-alkenyl glycines of type 10. The scope of this synthesis is limited by the fact that the compounds 9 are thermolabile when disubstitued at C-4. As for 23: The lithiated bis-lactim ether 6 is reacted with thioketones 14 to give the addition products 15 with de>95%. The S-methyl compounds 16 undergo elimination to give regioselectively the olefins 18 when treated with Raney-Ni. Alternatively, the olefms 18 are obtained from the sulfonium salts 24 by dimethyl sulfide elimination, although this route is less regiospecific. The compounds 18 are cleaved by dilute hydrochloric acid, liberating L-valinate 8 and (R)-α-alkenyl glycine methvl esters 21. which on further hvdrolvsis vield (R)-α-alkenyl glycines 23. This synthesis is limited only by the availability of thioketones 14.