This application seeks support for the chemical synthesis of oligonucleotides utilizing new phosphorylation methods developed under Grant GM20672. The reagents are pyrophosphate, phosphorochloridate and N-phosphoroimidazole derivatives of the 2-oxo-4,5-dimethyl-1,3,2-dioxyaphospholyl group, a cyclic enediol phosphoryl derivative. The reagents convert two alcohols, RlOH and R2OH into a triester, (RlO) R2O)P(O)OCH(CH3)COCH3 without the need for additional activating reagents, and using a minimum of protection of bases and sugar residues. The triesters are converted into the diesters, (RlO)(R2O)P(O)OH in a mild and efficient step. The goals of the research are: (1) The synthesis of t-RNA's anticodon triads and pentads in order to study problems of conformation and anticodon stem rigidity. (2) The synthesis of t-RNA's terminal triads and tetrads containing an aminoacylated terminal nucleoside in order to study aminoacylation-structure relationships at the amino acid stem. (3) The synthesis of mixed deoxyribo-oligonucleotides and ribo-arabo-oligonucelotides for studies on mechanisms of transcription and translation, and for antitumor drug studies.