BOC-L-Asparagine

To confirm a selectivity of 3-CD-histamine for substrates, experiments of the hydrolysis with 3-CD-histamine were made using several kinds of substrates as follows N-tert-butoxycarbonyl-L-glutamine-p-nitrophenyl ester (Boc-Gln-ONP), Boc-L-asparagine-p-nitrophenyl ester (Boc-Asn-ONP), Boc-Glycine-p-nitrophenyl ester (Boc-Gly-ONP), Boc-L-Leucine-p-nitrophenyl ester (Boc-Leu-ONP). In these cases, all hydrolytic reactions with 3-CD-histamine were detected as a reaction type of Michaelis-Menten mechanism. Catalytic rate constants in the hydrolysis with 3-CD-histamine are shown in Table 3. Compared with Boc-Gln-ONP and Boc-Asn-ONP, the structural difference is only one carbon in the side chain of amino acid. But reactivity (kcat/Km) is different about three times. In these four substrates, in the case of Boc-Asn-ONP, the re-... 

Table 3 Dehydration of Unprotected Asparagine During Coupling of Boc-Asn-OH to H-X-Peptidel l...

Higher yields of L-[amide- N]asparagine have been obtained by a rapid, nonenzymatic method. The free -carboxyl group of L-a-N-f-Boc-a-t-Bu-aspartic acid is activated with N-hydroxysuccinimide to yield L-a-N-f-Boc-a-t-Bu- -N-hydroxysuccinimidyl aspartic ester, which is re-fiuxed for 10 min with [ N]anunonia. Hydrolysis for 1 min in IN HCl yields up to 30-40% of L-[ami fe- N]asparagine, which is then purified by cation-exchange column chromatography (31). 

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