FLUOROCARBOCYCLIC NUCLEOSIDES - SYNTHESIS AND ANTIVIRAL ACTIVITY OF 2'-FLUOROCARBOCYCLIC AND 6'-FLUOROCARBOCYCLIC 2'-DEOXY GUANOSINES

A series of four isomeric 2'- and 6'-fluorocarbocyclic guanosine analogues have been prepared and evaluated as potential anti-herpes agents. The racemic 2'-beta-fluoro isomer 2-amino-1,9-dihydro-9-[(1-alpha, 2-alpha, 3-beta, 4-alpha)-2-fluoro-3-hydroxy-4-(hydroxymethyl)cyclopenty]-6H-purin-6-one (11a, C-AFG) and its 2'-alpha-fluoro epimer 11b plus the chiral 6'-beta-fluoro isomer 2-amino-1,9-dihydro-9-[[1S-(1-alpha, 2-alpha, 3-alpha, 4-beta)]-2-fluoro-4-hydroxy-3-(hydroxymethyl)cyclopentyl]-6H-purin-6-one (11c) and its 6'-alpha-fluoro epimer 11d were prepared from their respective fluoro amino diol hydrochlorides (6a,d). For comparison, the furanosyl compound 9-(2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl)guanine (17, AFG) was prepared by coupling 2-amino-6-chloropurine with 2-deoxy-2-fluoro-3,5-di-O-benzoyl-alpha-D-arabinofuranosyl bromide followed by base hydrolysis. The 6'-alpha-fluoro derivative 11d exhibited comparable activity to that of acyclovir (ACV) against herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) in vitro but was > 30-fold more active than ACV against HSV-1 and HSV-2 in vivo in the mouse systemic model. The 2'-beta-fluoro derivative (11a, C-AFG) was extremely potent in vitro against HSV-1 and HSV-2 (ID50 0.006 and 0.05-mu-g/mL) and in vivo it was greater than 2 orders of magnitude more potent than ACV against HSV-1 and 70-fold more potent against HSV-2. The 2'-alpha-fluoro 11b and 6'-beta-fluoro 11c isomers were much less active.