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Pure Appl. Chem., 2000, Vol. 72, No. 9, pp. 1763-1768

Versatility of β-lactams in synthesis. Studies directed toward the synthesis of complex nucleoside antibiotics and some macrocyclic peptides

Claudio Palomo, Jesús M. Aizpurua, Iñaki Ganboa and Mikel Oiarbide

Departamento de Química Orgánica, Facultad de Química, Universidad del País Vasco, Apdo 1072, 20080 San Sebastián, Spain

Abstract: The diastereoselective [2+2] cycloaddition of α-hydroxyketene equivalents with chiral α,ω-oxyaldehyde-derived imines followed by the 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO)-promoted ring expansion of the resulting α-hydroxy β-lactam adducts provides an unconventional and short route to α-amino acid N-carboxy anhydrides (NCAs). The required enantiopure α,ω-oxyaldehydes were obtained either from the chiral pool or through the Sharpless AD methodology. Following the present strategy, several nonproteinogenic NCAs were synthesized, which were further coupled with α-amino acid esters giving rise to key fragments of some nucleoside antibiotics and macrocyclic peptides.