L-Leucine → L-Leucine

Participants

Reaction Steps

A dipeptide of L-leucine and L-phenylalanine was prepared using the above described resin. N-(tert-butyloxycarbonyl)-L-leucine was coupled using the procedure of Example 1. Amino acid analysis of this resin showed a leucine content of 0.75 meq/g. When treated with 45% trifluoroacetic acid to deprotect and cap the residual sulfide as in Example 1, the leucine content dropped to 0.49 meq/g. A sample of this resin (0.994 g, 0.49 mmol) was washed twice with a solution of 10% diisopropyl ethylamine in methylene chloride, followed by three washes with methylene chloride to neutralize the resin. The resin was coupled with N(tert-butyloxycarbonyl)-L-phenylalanine by suspending the resin in 10 ml methylene chloride and adding 464 mg (1.75 mmol) N-(tert-butyloxycarbonyl)-L-phenylalanine and 0.27 ml (235 mg, 1.86 mmol) N,N-diisopropylcarbodiimide. After shaking for two hours, the resin was washed three times with methylene chloride and dried under vacuum. Amino acid analysis showed the leucine content to be 0.40 meq/g and the phenylalanine content to be 0.40 meq/g.

Provenance & Evidence