【摘要】 本文叙述的修饰核苷酸——假尿嘧啶核苷酸的合成以及它和胸腺嘧啶核苷酸的保护,酵母丙氨酸转移核糖核酸TψC臂中CpCpGpG和TpψpCpG的合成.CpCpGpG和TpψpCpG均已圆满地用于t-RNA_y^Ala的3’-半分子合成和整分子的全合成.更多还原

【Abstract】 Modified ribonucleotiede ψp and its oligoribonucleotides, ψpCpG, TpψpCpG as well as tetraribonucleoside triphosphate CpCpGpG located in the vicinty of the same TψC arm of t-RNA_y^Ala were synthesized.5’-O-Monomethoxytrityl-2’-O-benzoylpseudouridine 3’-phosphate（5） was synthesized by using 5’-O-monomethoxyltritylpseudouridine through successive phosphorylation with morpholinophosphodichloridate, cyclization with dilute alkali, digestion with pancreatic ribonuclease A and finally benzoylation with benzoylimidazole. The overall yield of 5 was about 40%.2’, 5’-O-Dibenzoylribothymidine 3’-phosphate （6） was prepared by benzoylation of ribothymidine 3’-phosphate with benzoylimidazole （yield about 80%）. ψpCpG （3） and TpψpCpG （1） were synthesized in the presence of DCC by stepwise condensation of appropriately protected monoribonucleotides, 5 and 6 with diribonucleoside monophosphate, C_bzp^bzG_ibu2^ibu（12） according to the synthetic scheme （Pig. 1） with yields of 35 and 25% respectively.Protected tetraribonucleoside triphosphate （MeOTr） C_bzp^bzC_bzp^bzG_ibup2^ac was synthesized by block condensation of （MeOTr） C_bzp^bzC_bzp^bz（4） with G_ibup^acG_ibu2^ibu（9） aocording to the synthetic scheme （Fig. 2）. After deprotecticn, OpOpGpG （2） was obtained （yield 17%）.All these oligoribonucleotides synthesized were homogeneous on paper chromatography and paper electrophoresis. The base ratios of the obtained individual oligoribonucleotide agreed with those of the expected oligoribonucleotides on the determination by RPC-5 column chromatography after digestion of the sample with pig spleen phosphodiesterase. The sequences of CpCpGpG and TpψpCpG were determined by two dimensional electrophoresis-homochromatography after laholling 5’-terminal hydroxyl group with (γ-³²P)ATP by polynucleotide kinase and partial hydrolysis with snake venom phosphodiesterase. The autoradio patterns are in accordance with those of the 5’-³²P-labeled oligoribonucleotides.The synthetic oligoribonucleotides, CpCpGpG and TpψpCpG, of which the ribonucleotide sequences corresponding to those of 50～53 and 54～57 fragments from the 5’-terminal of t-RNA_y^Ala molecule respectively, had been successfully used in the synthesis of dodecaribonucleotide GpUpCpUpCpCpGpGpTpψpCpG, 3’-terminal half molecule and the whole molecule of t-RNA_y^Ala.更多还原