104987-44-2 3'-(N-methyl-1,4-dihydronicotinoyl)-5'-pivaloyltrifluorothymidine DHTFT Thymidine, alpha,alpha,alpha-trifluoro-, 3'-(1,4-dihydro-1-methyl-3-pyridinecarboxylate) 5'-(2,2-dimethylpropanoate)