4,4'-双甲氧基三苯甲基氯   、                                                                                      
{9-{(2R,3R,4S,5R)-4-Hydroxy-5-hydroxymethyl-3-[2-(4-nitro-phenyl)-ethoxycarbonylamino]-tetrahydro-furan-2-yl}-6-[2-(4-nitro-phenyl)-ethoxy]-9H-purin-2-yl}-carbamic acid 2-(4-nitro-phenyl)-ethyl ester                                                                                                                                                              在
                                                                                                                                                                                 
吡啶   、                                                                                                  4 A molecular sieve                                                                                                                                  作用下,
                                                                                                                                                                                                                            以53%的产率得到{9-{(2R,3R,4S,5R)-5-[Bis-(4-methoxy-phenyl)-phenyl-methoxymethyl]-4-hydroxy-3-[2-(4-nitro-phenyl)-ethoxycarbonylamino]-tetrahydro-furan-2-yl}-6-[2-(4-nitro-phenyl)-ethoxy]-9H-purin-2-yl}-carbamic acid 2-(4-nitro-phenyl)-ethyl ester