Synthesis of AZT 5'-triphosphate mimics and their inhibitory effects on HIV-1 reverse transcriptase.
In search of active nucleoside 5'-triphosphate mimics, we have synthesized a series of AZT triphosphate mimics (AZT P3Ms) and evaluated their inhibitory effects on HIV-1 reverse transcriptase as well as their stability in fetal calf serum and in CEM cell extracts. Reaction of AZT with 2-chloro-4H-1,3,2-benzodioxaphosphorin-4-one, followed by treatment of the phosphite intermediate 2 with pyrophosphate analogues, yielded the cyclic triphosphate intermediates 4b-4f, which were subjected to boronation and subsequent hydrolysis to give AZT 5'-alpha-borano-beta,gamma-bridge-modified triphosphates 6b-6f in moderate to good yields. Reaction of the cyclic intermediate 4d with iodine, followed by treatment with a series of nucleophiles, afforded the AZT 5'-beta,gamma-difluoromethylene-gamma-substituted triphosphates (7b-7i). Several different types of AZT P3Ms containing alpha-P-thio (or dithio) and beta,gamma-difluoromethylene (13,14), alpha,beta-difluoromethylene and gamma-P-methyl(or phenyl) (15,16), and alpha-borano-beta,gamma-difluoromethylene and gamma-O-methyl/phenyl (11,12) were also synthesized. The effectiveness of the compounds as inhibitors of HIV-1 reverse transcriptase was determined using a fluorometric assay and a poly(A) homopolymer as a template. A number of AZT P3Ms exhibited very potent inhibition of HIV-1 reverse transcriptase. Modifications at the beta,gamma-bridge of triphosphate rendered the AZT P3Ms 6b-6f with varied activities (K(i) from 9.5 to >>500 nM) while modification at the alpha,beta-bridge of triphosphate led to weak AZT P3M inhibitors. The results imply that the AZT P3Ms were substrate inhibitors, as is AZT triphosphate. The most active compound, AZT 5'-alpha-R(p)()-borano-beta,gamma-(difluoromethylene)triphosphate (AZT 5'-alphaB-betagammaCF(2)TP) (6d-I), is as potent as AZT triphosphate with a K(i)() value of 9.5 nM and at least 20-fold more stable than AZT triphosphate in the serum and cell extracts. Therefore, for the first time, a highly active and stable nucleoside triphosphate mimic has been identified, which is potentially useful as a new type of antiviral drug. The promising triphosphate mimic, 5'-alpha-borano-beta,gamma-(difluoromethylene)triphosphate, is expected to be valuable to the discovery of nucleotide mimic antiviral drugs.
Wang
Guangyi
G
Research Laboratories, Biota, Inc., 2232 Rutherford Road, Carlsbad, CA 92008, USA. g.wang@biota-inc.com
Boyle
Nicholas
N
Chen
Fu
F
Rajappan
Vasanthakumar
V
Fagan
Patrick
P
Brooks
Jennifer L
JL
Hurd
Tiffany
T
Leeds
Janet M
JM
Rajwanshi
Vivek K
VK
Jin
Yi
Y
Prhavc
Marija
M
Bruice
Thomas W
TW
Cook
P Dan
PD
D004355:Drug Stability; D054303:HIV Reverse Transcriptase / Q000037:antagonists & inhibitors*; D006801:Humans; D018894:Reverse Transcriptase Inhibitors / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D013329:Structure-Activity Relationship; D015215:Zidovudine / Q000031:analogs & derivatives*
D018894:Reverse Transcriptase Inhibitors; D015215:Zidovudine; D054303:HIV Reverse Transcriptase