Syntheses of Enantiomerically Pure a-Amino Acids

The hydrolysis of the pure 7 -aminonitriles 8a with HC1 and formic acid or HBr in acetic acid leads to the free D-amino acids 9 without racemization in high yields. 

L-Amino acids 11 are available by the same methodology using tri-0-pivaloyl-a-D-arabinosylamine 10 as the chiral auxiliary [19b], The stereoselectivity L D 7-10 1 is slightly lower compared to that observed for the syntheses of / -aminonitriles 8 with galactosyl imines 7. The free a-amino acid is released from the auxiliary by hydrolysis with HCI in formic acid. 

The Ugi reaction provides another access to a-amino acid derivatives [25]. This important multicomponent reaction will be discussed in Section 4.2.4. 

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