A simple and efficient protocol for the preparation of 7-substituted purines is described. 6- and 2,6-Dihalopurines were N(9)-tritylated and then transformed to 7,8-dihydropurines by DIBAL-H. Subsequent N(7)-alkylation followed by N(9)-trityl deprotection with trifluoroacetic acid was accompanied by spontaneous reoxidation, which led to the 7-substituted purines at 55-88% overall isolated yields.

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Selective Synthesis of 7-Substituted Purines via 7,8-Dihydropurines. -The one-pot procedure starting from halopurines (I) or (VI) involves only two separation steps. The regioselectively N 9 -trityl-protected purines obtained by the first step and the final products are isolated by chromatography, the intermediates formed by the reduction and alkylation step are employed directly. The trityl-deprotection by TFA is accompanied by spontaneous oxidation affording the desired 7-substituted purines like (III) and (VIII). -(KOTEK, V.; CHUDIKOVA, N.; TOBRMAN, T.; DVORAK*, D.; Org. Lett. 12 (2010) 24, 5724-5727, http://dx.doi.org/10.1021/ol1025525 ; Inst. Org. Chem., Prague Inst. Chem. Technol., CZ-166 28 Prague 6, Czech Republic; Eng.) -Klein 12-166

Regioselective and Efficient Synthesis of N 7 -Substituted Adenines, Guanines, and 6-Mercaptopurines. -(MARYSKA, M.; CHUDIKOVA, N.; KOTEK, V.; DVORAK, D.; TOBRMAN*, T.; Monatsh. Chem. 144 (2013) 4, 501-507, http://dx.doi.org/10.1007/s00706-012-0899-x ; Dep. Org. Chem., Prague Inst. Chem. Technol., CZ-166 28 Prague 6, Czech Republic; Eng.) -H. Toeppel 32-184