Five-membered azasugars possessing N-alkyl and C₁ alkyl substituents constitute a class of potent antiviral compounds active against hepatitis B virus (HBV), hepatitis C virus (HCV), and human immunodeficiency virus (HIV). Recently we observed enhanced antiviral activity attendant the presence of both an N-alkyl group as well as a C₁ dialkyl group. We report now a general synthesis of five-membered azasugars possessing both N-alkyl group and C₁ geminal dialkyl groups. Thus starting with L-lyxonolactone the series of analog I was obtained. Members of the enantiomeric series of compounds have been made in the D-lyxo → L-ribo series (II). The antiviral activity of these new iminocyclitols in the bovine viral diarrhoea virus assay (BVDV) will be presented.