Synthesis and HIV-1 reverse transcriptase inhibition of 3′-azido-3′,5′-dideoxythymidine 5′-methylphosphonic acid diphosphate : G. A. Freeman∗†, J. L. Rideout†, and W. H. Miller≠. Burroughs Wellcome Co., †Division of Organic Chemistry and ≠Division of Experimental Therapy, 3030 Cornwallis Rd., Research Triangle Park, N. C. U.S.A.