Synthesis of [2-13C, 4-13C]-(2R,3S)-catechin and [2-13C, 4-13C]-(2R,3R)-epicatechin

The first synthesis of doubly labeled, [2-C-13, 4-C-13]-(2R,3S)-catechin 15 and [2-C-13, 4-C-13]-(2R,3R)-epicatechin 18 starting from labeled 2-hydroxy-4, 6-bis(benzyloxy)acetophenone 3 and labeled 3, 4-bis(benzyloxy)-benzaldehyde 7 are described.