Trifluoroacetic acid → methyl D-isoglutaminate trifluoroacetic acid salt

Participants

Reaction Steps

Methyl t-butyloxycarbonyl-D-isoglutaminate (651 mg, 2.5 mmol) was treated with cold trifluoroacetic acid (5 ml) in a similar manner to that described in Example 33 (IV) to obtain methyl D-isoglutaminate trifluoroacetic acid salt. This salt was then dissolved in ethyl acetate (5 ml), and neutralized by adding TEA (0.35 ml) with cooling. To the resulting solution was added a solution of t-butyloxycarbonyl-O-benzyl-L-serine HONB active ester in ethyl acetate (5 ml), and the reaction was carried out at room temperature for 16 hours. The work-up similar to that described in Example 33 (I) and recrystallization from ethyl acetate/ether gave methyl t-butyloxycarbonyl-O-benzyl-L-seryl-D-isoglutaminate (0.78 g). m.p. 103°-104° C. [α]D22 +7.0 (C 0.5, ethanol). Rf5 =0.40.

Provenance & Evidence