Purines. LIV. Intramolecular Cyclization of 9-Ethyl-1-(2-hydroxyethyl)adenine Caused by Nucleophiles: Formation of N6, 1-Ethanoadenine Derivatives.
作者:Tohru SAITO、Miyoko MURAKAMI、Tadaaki INADA、Hiromi HAYASHIBARA、Tozo FUJII
DOI:10.1248/cpb.41.453
日期:——
Treatment of 9-ethy-1-(2-hydroxythyl)adenide hydrobromide (1a) in boiling N, N-dimethylformamide (DMF) with an excess of thiourea for 7 h or with an excess of ammonium thiocyanate for 3 h provided 3-ethyl-7, 8-dihydro-3H-imidazo[2, 1-i]purinium thiocyanate (8) in 51% or 58% yield, respectively. On treatment with an excess of triphenyl phosphite in boiling DMF for 20 min, 1 a underwent a similar cyclization to from the same tricycle, which was isolated in 81% yield (from 1 a)in the form of the perchlorate salt (12). A similar treatment of 1 a with triethyl phosphite furnished the 9-ethyl analogue (15) in 83% yield. Conversion of 12 into the free base and oxidation of latter with active MnO2 in boiling CH2Cl2 for 16 h gave 3-ethyl 3-ethyl-3H-imidazo[2, 1-i]purine (13) (66% overall yield from 12), which was identical with a sample synthesized from 9-ethyladenine (9) and chloroacetaldehyde according to the general N6, 1-etheno bridgeing procedure. On treatment with methanolic ammonia at room temperature, the tricycle 15 afforded 9-ethyl-N6-[2-(ethylamino)ethyl]adenine hydrobromide (26) in 79% yield. Mechanisms are proposed for the above intramolecular cyclizations of 1 a caused by the S- and P-atom nucleophiles.
在沸腾的N,N-二甲基甲酰胺(DMF)中,将9-乙基-1-(2-羟乙基)腺嘌呤氢溴酸盐(1a)与过量的硫脲反应7小时,或与过量的硫氰酸铵反应3小时,分别以51%或58%的产率得到3-乙基-7,8-二氢-3H-咪唑并[2,1-i]嘌呤硫氰酸盐(8)。在沸腾的DMF中,将1a与过量的三苯基膦反应20分钟,经历类似的环化反应,生成相同的 Tricycle,以81%的产率(从1a开始)分离得到高氯酸盐形式(12)。将1a与三乙基膦反应得到9-乙基类似物(15),产率为83%。将12转化为自由碱,并在沸腾的CH2Cl2中用活性MnO2氧化16小时,得到3-乙基-3H-咪唑并[2,1-i]嘌呤(13)(从12开始的总产率为66%),与根据N6,1-乙烯桥接法由9-乙基腺嘌呤(9)和氯乙醛合成的样品相同。在室温下用甲醇氨处理三环化合物15,以79%的产率得到9-乙基-N6-[2-(乙胺基)乙基]腺嘌呤氢溴酸盐(26)。上述1a分子内环化过程由S和P原子亲核试剂引起的机制被提出。