2.6- Dimethyl-5-phenyl-2,3-dihydropyrazine

An excellent source of readily available chiral auxiliaries is to be found in amino-acids, and Schollkopf and co-workers have once again used them to prepare lithiated dihydropyrazines (11). In particular, they have used L-valine, tert-leucine, and (5)-0,0-dimethyl-a-methyldopa in the synthesis of (i )-a-amino-acids from, for example, glycine. "" The same authors have also used the oxazinones (12) to give chiral (S )-a-alkyl-a-phenylglycines from DL-phenyl-glycines however, in this case 2-hydroxyalkanoic acids are used as the chiral auxiliaries. In a quite different approach, protected and lithiated glycine is converted into alanine by the methyl sulphate (13) in enantiomeric excesses approaching 40... 

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