A novel diastereoselective α-functionalization of proline with benzaldehydes: synthesis of α-(α-hydroxybenzyl)prolines

2-Oxapyrrolizidines formed in reactions of methyl prolinate with two molecules of aromatic aldehyde upon gradual hydrolysis give α-(α-hydroxybenzyl)prolines. The products are preferentially formed as one diastereomer (91–100%) in overall yield 33–50% (five stages starting from proline).