A highly efficient flow reactor process for the synthesis of N-Boc-3,4-dehydro-L-proline methyl ester

The multi-step preparation of N-Boc-3,4-dehydro-L-proline methyl ester using a modular flow reactor is reported. The use of immobilised reagents and scavengers in pre-packed glass tubes allows us to obtain the pure product in 87% overall yield, 97% purity, and >98% enantiomeric excess without any additional purification step. Our flow-based protocol enables the rapid multi-gram synthesis (about 9 g/12 h) of the desired product. (C) 2010 Elsevier Ltd. All rights reserved.