合成路线1

Protection of the chiral aza-sugar (XIV) using Boc2O in MeOH provides the corresponding N-Boc derivative (XV) , which by oxidative cleavage of the vicinal diol with NaIO4, and subsequent reductive treatment with NaBH4 in EtOH leads to 1-Boc-3(R)-hydroxy-4(R)-(hydroxymethyl) pyrrolidine (XII). Protection of both hydroxyl groups of compound (XII) using PhCH2Br and NaH in DMF, followed by acidic cleavage of the Boc group, the resulting dibenzyl ether using methanolic HCl provides the protected pyrrolidine (XVI) . Reductive condensation of pyrrolidine (XVI) with the deazapurine aldehyde derivative (XVII) [obtained by metalation of the bromodeazapurine derivative (XVIII) with butyllithium in Et2O/PhOMe or THF at −78 °C, followed by quenching with DMF] using NaBH3CN in MeOH yields the fully protected compound (XIX) . Finally, selective cleavage of the t-butyl ether of (XIX) by means of HCl in MeOH or TFA in CH2Cl2 affords intermediate (XIII) .