7-Allyl-8-oxoguanosine (loxoribine, 5) was selected from a series of g
uanosine derivatives for further evaluation as an immunostimulant. Num
erous related analogs were also synthesized and evaluated: 2',3'-ketal
s of 5 are particularly interesting because they are active, apparentl
y without being cleaved to the free nucleoside.