A convenient method of synthesizing a tripeptide-containing N-methyl group amino acid was developed using O-benzotriazole-N,N,N',N'-tetramethyluronium-hexafluorophosphate as the condensing agent. The crystals of tripeptide had white needles belonging to the orthorhombic space group P2_12_12_1. The conformational preference for homochiral tripeptides with one N-methylated amide bond was also investigated. Crystal-structure analysis showed that homochiral tripeptides with an internal N-methylated amide bond preferred a trans-amide form, thereby giving the peptide β-fold characteristics. Intermolecular C–H···O and N–H···O hydrogen bonds linked the molecules into a one-dimensional chain and stabilized the structure.
设计了一种新颖实用的制备L-别苏氨酸和D-别苏氨酸的方法。以α-C消旋的N-乙酰化苏氨酸为原料,用L-(或D-)氨基酰化酶拆分相应的底物得到了高光学纯度的L-别苏氨酸(或D-别苏氨酸)。为了获得较高收率,考查p H,温度,Co2+浓度对拆分反应的影响。确定最优条件为:p H 7.5,温度37℃,Co2+浓度0.1 g·L-1。反应产率达到93.8%(L-allo-Thr)、89.8%(D-allo-Thr),de>99%。该方法具有立体选择性高,操作简单,反应条件温和的优点。
