O-TBDPS-D-Thr-N-Boc-L-tert-Leu-Diphenylphosphine (CAS# 1264520-63-9) is an organic phosphine-based catalyst used in enantioselective cycloaddition reactions, such as the [3+2] annulation of allenoates with imine or the [2+4] cycloadditon synthesis of pyrrolidin-2-one fused dihydropyrans.