Chiral Nickelacycles as Amino Acid Synthons

DEVELOPMENT OF CHIRAL NICKELACYCLES AS AMINO ACID SYNTHONS 

Because of the lack of reactivity of anhydrides with Pd(0) complexes, we turned to the more nucleophilic Ni(0) complexes. A number of N-protected anhydrides were chosen to study the regioselectivity and functional group compatibility in metallacycle formation. The effect of 

The best results were obtained by using the phthaloyl derivative (+)63 because this protective group allows the regioselective preparation of both a- and P-phthaloyl alanines by simply changing the ligand on nickel (Entries 9 and 11). Furthermore, with this protective group the decar- 

Notes Yields were determined by NMR. The only other constituent of the crude reaction mixture was the N-protected aspartic acid. 

Similar results were achieved with glutamic acid anhydrides 64 and 65 (Table 2). However, although legioselective formation of a-ami-nobutyric acid was possible (Entries 1, 2, and 4), the formation y-ami-nobutyric acids proceeded with only moderate regioselectivity (Entry 6). 

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IV. DEVELOPMENT OF CHIRAL NICKELACYCLES AS AMINO ACID SYNTHONS... 

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