Synthesis and enantioselectivity of cyclopropavir phosphates for cellular GMP kinase

Abstract

Enantiomeric cyclopropavir phosphates (+)-9 and (-)-9 were synthesized and investigated as substrates for GMP kinase. N(2)-Isobutyryl-di-O-acetylcyclopropavir (11) was converted to (+)-monoacetate 12 using hydrolysis catalyzed by porcine liver esterase. Phosphorylation via phosphite 13 gave after deacylation, phosphate (+)-9. Acid-catalyzed tetrahydropyranylation of (+)-monoacetate 12 gave, after deacylation, tetrahydropyranyl derivative 14. Phosphorylation via phosphite 15 furnished, after deprotection, enantiomeric phosphate (-)-9. Racemic diphosphate 16 was also synthesized. The phosphate (+)-9 is a relatively good substrate for GMP kinase with a K(M) value of 57 microM that is similar to that of the natural substrates GMP (61 microM) and dGMP (82 microM). In contrast, the enantiomer (-)-9 is not a good substrate (K(M) 1200 microM) indicating a significant enantioselectivity for the GMP kinase catalyzed reaction of monophosphate to diphosphate.

Figures

FIGURE 1

Time course of phosphorylation of enantiomeric cyclopropavir phosphates (+)-9 and (−)-9 catalyzed by GMP kinase.

SCHEME 1

Phosphorylation cascade of ganciclovir (5).

SCHEME 2

Synthesis of cyclopropavir phosphate (+)-9 (i-But, isobutyryl; THP, tetrahydropyranyl; COIm2, N,N′-carbonyldiimidazole).

SCHEME 3

Synthesis of cyclopropavir phosphate (−)-9 (i-But, isobutyryl; THP, tetrahydropyranyl; COIm2, N,N′-carbonyldiimidazole).

SCHEME 4

Synthesis of racemic cyclopropavir diphosphate 16 (i-But, isobutyryl; THP, tetrahydropyranyl; COIm2, N,N′-carbonyldiimidazole).

CHART 1