Saxagliptin Intermediate 1

Ethyl N-Boc-L-proline-4-ene

ethyl N- Boc- 4,5- dehydroprolinate

(S)-1-Boc-2,3-dihydro-2-pyrrolecarboxylic acid ethyl ester

(S)-1-tert-Butyl 2-ethyl 2,3-dihydro-1H-pyrrole-1,2-dicarboxylate