A general and convenient synthesis of 7-alkyladenines from adenine by regioselective alkylation utilizing blocking/deblocking at the 3-position.
作者:NELSON J. LEONARD、TOZO FUJII、TOHRU SAITO
DOI:10.1248/cpb.34.2037
日期:——
A detailed account is given of the final step of the general 7-alkalation procedure for adenine (1), which consists of the preferential benzylation at the 3-position of 1, regioselective alkylation of the resulting 3-benzyladenine (2) to give 7-alkyl-3-benzyladenine salts (3a-c), and debenzylation of 3a-c leading to 7-alkyladenines (4a-c). Debenzylation of 3a-c (X=Cl or ClO4) has been achieved by hydrogenolysis using hydrogen and Pd-C catalyst at atmospheric pressure, producing 7-alkyladenines (4a-c) in 38-74% yields. The use of the allyl or γ, γ-dimethylallyl group at the 3-position instead of the benzyl group for the synthesis of 7-methyladenine (4a) by this procedure has no practical value. Alternatively, the salts 3a-c (X=Br, ClO4, or I) have been debenzylated efficiently by treatment with conc. H2SO4 in the presence of toluene at room temperature for 3-6h or at 60°C for 0.5-2h, giving 4a-c in 73-93% yields.
详细描述了腺嘌呤(1)的通用7-烷基化程序的最后一步,包括优先在1的3-位进行苄基化,对生成的3-苄基腺嘌呤(2)进行区域选择性烷基化,得到7-烷基-3-苄基腺嘌呤盐(3a-c),以及对3a-c进行脱苄基化,产生7-烷基腺嘌呤(4a-c)。通过在常压下使用氢气和Pd-C催化剂进行氢解,已经实现了3a-c(X=Cl或ClO4)的脱苄基化,产率38-74%。通过这一程序,在3-位使用烯丙基或γ, γ-二甲基烯丙基而不是苄基来合成7-甲基腺嘌呤(4a)没有实际价值。或者,通过在甲苯存在下于室温处理3-6小时或于60°C处理0.5-2小时,使用浓H2SO4有效地进行脱苄基化,盐3a-c(X=Br、ClO4或I)产率73-93%。