The total synthesis of the octacosapeptide corresponding to the proposed primary structure of porcine somatostatin-28, a possible precursor of somatostatin, is described. The primary structure of somatostatin-28 corresponds to that of somatostatin elongated at the N-terminus by a tetradecapeptide sequence. The synthesis has been performed using the strategy of overall acid labile side chain protection based on tert-butanol and adamantol derived protecting groups in combination with the S-tert-butylthio group for the reversible blocking of the cysteine thiol functions and the Nα -2-nitrophenylsulfenyl group for the chain elongation steps. Upon assembly in sequence order of the four suitably protected fragments related to sequence 18-28, 15-17, 8-14 and 1-7, respectively, reductive cleavage of the S-tert-butylthio groups from the fully protected octacosapeptide, followed by acidolytic deprotection via exposure to trifluoroacetic acid and subsequent air oxidation led to crude somatostatin-28. Purification by gel filtration on Biogel P 6 and ion exchange chromatography on Biogel CM 2 produced the desired product in satisfactory yields and at a high degree of purity as judged from different analytical tests. The correctness of the proposed primary structure was ultimately proofed by comparative analysis of the synthetic and natural product by means of chromatographic, immunological and biological assays
描述了与猪
生长抑素-28的拟议主要结构相对应的八十八肽的全合成,这可能是
生长抑素的前体。
生长抑素-28的主要结构相当于在N-末端延长了一个十四肽序列的
生长抑素。合成采用了基于
叔丁醇和
金刚烷基保护基的总体酸敏侧链保护策略,结合S-叔丁基
硫基团用于可逆阻断半胱
氨酸巯基功能和N
α -2-
硝基苯硫基团用于链延长步骤。按照与序列18-28、15-17、8-14和1-7相关的四个适当保护的片段的顺序组装,从完全保护的八十八肽中还原性裂解S-叔丁基
硫基团,随后通过
三氟乙酸暴露和随后的空气氧化的酸解保护,得到粗
生长抑素-28。通过Biogel P 6凝胶过滤和Biogel CM 2离子交换色谱纯化,以满意的产率和高纯度获得所需产品,从不同的分析测试结果来看。通过色谱、免疫学和
生物学测定的比较分析,最终证实了拟议的主要结构的正确性。