7H-Purine, 2,6-dichloro- 7-[2-deoxy-3,5-O-bis(4-methylphenyl)- .beta.-D-ribofuranosyl]- 7H-Purine, 2,6-dichloro- 7-[2-deoxy-3,5-O-bis(4-methylphenyl)-.beta.-D-erythropentofuranosyl]- NSC685833