4.1.39  (2R,5R)-2-(6-amino-9H-purin-9-yl)-5-{[(2-{[(2R,5R)-2-(6-amino-9H-purin-9-yl)-4-hydroxy-5-(hydroxymethyl)oxolan-3-yl]oxy}ethyl)[(4-chlorophenyl)methyl]amino]methyl}oxolane-3,4-diol (16)