TOTAL SYNTHESIS OF HUMAN INSULIN .4. DESCRIPTION OF FINAL STEPS
TOTAL SYNTHESIS OF HUMAN INSULIN .4. DESCRIPTION OF FINAL STEPS
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DOI：
10.1002/hlca.19770600105
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发表时间：
1977-01-01
影响因子：
1.8
通讯作者：
RITTEL, W
中科院分区：
文献类型：
--
作者：
SIEBER, P;KAMBER, B;RITTEL, W
最近对人胰岛素的一条新的合成途径作了初步介绍。在本报告中，这一综合的最后步骤，即，从不对称胱氨酸衍生物I中分离得到。I含有通过二硫桥A20-B19连接的序列A（14-21）和B（17-30）。这些最后的步骤是：在三氟乙醇中通过pH控制的酸解选择性除去N（α）- Trt [三苯基甲基]，通过与片段B（1-16）偶联完成B链，通过三氟乙醇选择性除去N（α）- Bpoc [2-（对联苯基）-异丙氧基羰基]，通过与环状片段A（1-13）偶联完成A链，除去酸不稳定的保护基，并通过用I.由反应混合物的组成判断，85元环的闭合以超过70%的环化产率进行。从合成的最后一步，通过逆流分布进行广泛纯化后获得2种产物：产率为50%的纯人胰岛素及其产率为25%的[D-酪氨酸B16]异构体。虽然酪氨酸B16在与序列B（1-16）偶联期间发生部分外消旋化，但[D-酪氨酸B16]-立体异构体只能在终产物阶段分离。现有的证据表明，二硫键A7-B7的容易形成并不取决于已经具有胰岛素样构象的前体分子。
A preliminary account of a new synthetic pathway leading to human insulin was recently given. In this report the last steps of this synthesis, i.e., from the unsymmetrical cystine derivative I, are described in detail. I contains the sequences A(14-21) and B(17-30) linked by the disulfide bridge A20-B19. These last steps are: selective removal by pH-controlled acidolysis in trifluoroethanol of N(.alpha.)-Trt [triphenylmethyl] from leucine B17, completion of the B-chain by coupling with the fragment B(1-16), selective removal by trifluoroethanol of N(.alpha.)-Bpoc [2-(p-biphenylyl)-isopropyloxycarbonyl] at tyrosine A14, completion of the A-chain by coupling with the cyclic fragment A(1-13), removal of the acid labile protecting groups and formation of the disulfide bond A7-B7 from the 2 S-acetamido-protected cysteine residues by treatment with I. As judged by the composition of the reaction mixture, the closure of the 85-membered ring proceeds with a cyclization yield of over 70%. From the last step in the synthesis 2 products were obtained after extensive purification by counter-current distribution: pure human insulin in a yield of 50% and its [D-tyrosine B16]Isomer in a yield of 25%. Although the partial racemization of tyrosine B16 occurred during coupling with sequence B(1-16), the [D-tyrosine B16]-stereoisomer could only be separated at the endproduct stage. The available evidence indicates that the ease of formation of the disulfide bond A7-B7 does not depend on the precursor molecule already having an insulin-like conformation.