Hydrochloric Acid → Boc-Thr(Bzl)-Ser(Bzl)-Ser(Bzl)-Glu(OBzl)-OH

Participants

Reaction Steps

Boc-Ser(Bzl)-Ser(Bzl)-Glu(OBzl)-OH (71.6 g, 104 mmol) was treated with 2.7 liters of freshly prepared 3.9 N HCl in THF for 45 minutes. The mixture was evaporated to dryness and the residue evaporated twice more with THF to give a solid mass (59.3 g; mp 161°-165°). It was collected and washed with ether and stirred in 500 ml of DMF with Boc-Thr(Bzl)-OSu (38.2 g, 94 mmol) in the presence of Et3N (25 ml) at 0° for 1 hour and then at 25° for 15 hours. More Et3N (14.5 ml) was added in serveral portions during this time to maintain the reaction slightly basic. Some insoluble matter formed was filtered off and the filtrate evaporated to an oil which was dissolved in EtOAc (1.5 liters), washed with 5% HOAc, H2O (2 times), dried (Na2SO4), and evaporated to a solid mass. The product was recrystallized from EtOAc and petroleum ether to yield, 64.8 g (78.1%); mp 115°-118°; [α]D25 =+11.64° (c 1, DMSO).

Provenance & Evidence