The invention provides general methods for preparing 2,9-, 2,6,9-, O6-aryl- and O6-alkyl-substituted purines in a combinatorial and traceless fashion. The methods involve, in some embodiments, Mitsunobu alkylation of 2-fluoro-6-phenylsulfenylpurine at N9 with alcohols in solution, followed by C2-capture of the purine core with a resin-bound amine and subsequent oxidation and displacement of the C6 sulfonyl group with amines and anilines.