【摘要】 已知合成的胰岛素A链羧端带保护基的十二肽酯Ⅰ在不同条件下皂化,得十二肽Ⅱ,其物理性质略有差异,经制成牛胰岛素A链井进一步制成半合成牛胰岛素粗产物后,其生物活力相当于天然胰岛素的1—4％。根据二条不同的路线直接合成了带保护基的胰岛素A链羧端十二肽Ⅱ,路线一:由已知的四肽Ⅲ制成其酰肼衍生物,再转变为相应的迭氮化物后与脱N-苄氧羰基和γ-叔丁基的五肽Ⅴ(即Vb)缩合成九肽Ⅵ,Ⅵ经脱除N-保护基后与已知的三肽酰肼Ⅶ以迭氮化物法缩合郎得十二肽Ⅱ.路线二:三肽酰肼Ⅶ先制成迭氮化物再与脱N-保护基的已知二肽酯ⅩⅩⅢ反应成五肽酯ⅩⅩⅣ,再经肼解得五肽酰肼ⅩⅩⅤ,然后按迭氮化物法与脱苄氧羰基的二肽Ⅹ缩合成七肽酯ⅩⅩⅥ,再肼解得七肽酰肼ⅩⅩⅦ,最后通过迭氮化物法与五肽V_b缩合,亦得相同的十二肽Ⅱ.由这两种方法直接合成的十二肽Ⅱ,其质量较皂化所得为优,并已用于牛胰岛素A链的合成与结晶牛胰岛素的半合成和全合成。五肽Ⅴ和七肽ⅩⅩⅥ都曾各按二条不同的路线合成,而得到相同的产物,本文报导的合成肽段均经分析证明为化学纯的均一物质。更多还原

【Abstract】 Dodecapeptide ester Ⅰ has been saponified to give a protected C-terminal dodecapeptide （Ⅱ） of the A-Chain of insulin. Further experiments showed that the saponification of ester Ⅰ under various conditions yielded preparations of dodecapeptide Ⅱ varying somewhat in melting points and solubility. These saponification products have been used for the partial synthesis of bovine insulin and all the crude hormone products obtained showed biological activity of 1—4％ of natural insulin in mouse convulsion test. In order to avoid the saponification dodecapeptide Ⅱ has been directly synthesized by two alternative routes. By route 1, the known tetrapeptide Ⅲ was first converted into its hydrazide （Ⅳ）, which was then coupled by the azide method with pentapeptide V_b to form nonapepfide Ⅵ (C₆₆H₈₆N₁₂O₁₉S·2H₂O, m.p. 235—236° （decomp.）, [α]_D¹⁵—44° （c 1.0, DMF）). Nonapeptide Ⅵ was decarbobenzoxylated and combined with the known tripeptide hydrazide Ⅶ through the azide method to give dodecapeptide Ⅱ(C₈₄H₁₁₁N₁₅O₂₃S₂·2H₂O, m.p. 246—248°, [α]_D¹⁵—34° （c 1.0, HCOOH）). Pentapeptide V_b was prepared from pentapeptide V which was obtained by the following ways: （1） The known dipeptide ⅩⅢ was decarbobenzoxylated and the N-deblocked product was combined with dipeptide hydrazide ⅩⅣ by the azide method to form tetrapeptide XV (C₃₅H₄₀N₆O₁₀S·H₂O, m.p. 191—193°, [α]_D²¹-41° （c 1.0, DMF）). The same product has also been synthesized by coupling N-carbobenzoxy-L-asparagine p-nitrophenyl ester with N-deblocked tripeptide ⅩⅧ. Compound ⅩⅧ was in turn prepared from the condensation of N-carbobenzoxy-L-tyrosyl hydrazide with N-deblocked dipeptide ⅩⅢ (m.p. 188—190°, [α]_D³⁰-34° （c 1.0, DMF）). Tetrapeptide ⅩⅣ was further decarbobenzoxylated and the resulting product was condensed with α-p-nitrophenyl-γ-tert-butyl N-carbobenzoxy-L-glutamate （ⅩⅦ） to yield pentapeptide Ⅴ (C₄₄H₅₅N₇O₁₃S·H₂O, m.p. 185—186°, [α]_D²²-37° （c 2.0, DMF）). Both compounds ⅩⅧ and ⅩⅤ have been prepared by another method. （2） N-deblocked dipeptide ⅩⅥ was first coupled with ⅩⅦ to give tripeptide ⅩⅪ (m.p. 179—180°, [α]_D³²+7° （c 1.0, DMF）), which was then converted into its hydrazide ⅩⅫ (m.p. 219—220°,[α]_D³²—16.5° （c 1.0, DMF）). Hydrazide ⅩⅫ was finally condensed by the azide method with dipeptide ⅩⅢ to yield pentapeptide V. It seems that way （1） led to better overall yield and higher quality of the pentapeptide. By route 2, dodecapeptide Ⅱ was synthesized by condensing heptapeptide hydrazide ⅩⅩⅦ with pentapeptide V_b through the azide method. Hydrazide ⅩⅩⅦ (C₅₂H₇₄N₁₀O₁₂S·H_δO, m.p. 253—254° （decomp.）, [α]_D²⁶-36° （c 0.93, HCOOH）) was prepared from heptapeptide ester ⅩⅩⅥ. Ester ⅩⅩⅥ was synthesized by two alternative methods. In one of these methods tripeptide hydrazide Ⅶ was transformed into its azide and condensed with decarbobenzoxylated dipeptide ester ⅩⅩⅢ to form pentapeptide ester ⅩⅩⅣ (C₄₃H₅₇N₅O₁₀S·H₂O, m.p. 220—222°,[α]_D¹⁵-21° （c 1.0, DMF）), which was then converted into its hydrazide ⅩⅩⅤ and finally coupled through the azide method with N-deblocked dipeptide Ⅹ to give heptapeptide ester ⅩⅩⅥ (C₅₃H₇₄N₈O₁₃S·H₂O, m.p. 249—250° （decomp.）, [α]_D¹⁵-34° （c 1.0, DMF）). In the other method, ester ⅩⅩⅥ was obtained from tripeptide hydrazide Ⅶ and N-deblocked tetrapeptide Ⅲ by the azide method. All synthetic peptide intermediates have been subjected to elementary analyses, as well as paper chromatographic and paper electrophoretic examinations, and dodecapeptide Ⅱ has been analysed for its amino acid composition. The results showed that all synthetic peptides are chemically pure and homogeneous. Dodecapeptide Ⅱ prepared by the above routes has higher melting point and levorotatory power than that obtained by the saponification of ester Ⅰ. It has been used for the partial as well as total synthesis of crystalline bovine insulin.更多还原