Chemical modification of spiramycins. I. Synthesis of the acetal derivatives of neospiramycin I

Tetrahydrofuranyl and tetrahydropyranyl derivatives of neospiramycin I at 3 and/or 4' position were synthesized. In vitro and in vivo activities of these derivatives were correlated with the position and configuration of acetal groups. The most effective derivative, 3-a, 4'-a-di-O-tetrahydrofuranylneospiramycin I was comparable to spiramycin I.