The preparation of carbocyclic 4-deazaformycin and its 5′-homoanalogue
from a common vinyl precursor, and its N-1 and N-2 methyl derivatives
is reported. The syntheses began with a highly stereoselective SN2
reaction between lithio 4-picolines and a protected 2,3-dihydroxy-4-vinylcyclopentyl
triflate. The requisite fused pyrazole ring was created by an intramolecular
diazonium reaction that was followed by vinyl transformation into
the hydroxymethyl and the hydroxyethyl groups. The N-methyl derivatives
arose by standard methylation conditions and the resultant N-Me regiochemistry was assigned by homo-
and heteronuclear NMR spectroscopy.
C-nucleosides - carbocyclic nucleosides - pyrazolo[3,4-c]pyridines