NOVELTY - Preparing a ribonolactone (I) comprises reacting fructosamine compounds (II) in the presence of a calcium salt in a non-aqueous reaction medium, to provide (I).    USE - The process is useful for preparing a ribonolactone (claimed) which is used as an intermediate in the preparation of nucleosides and their derivatives including compounds having antiviral activity and anticancer activity, preferably anti-hepatitis C compound i.e. (2S)-2,2-dimethylpropyl 2-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3,4-dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy)(naphthalen-1-yloxy)phosphorylamino)propanoate.    ADVANTAGE - The process: provides (I) in a scalable to large scale production in a pilot or manufacturing plant and with improved yields; does not utilize strong base; utilizes lower levels of calcium containing materials to reduce calcium ion that is removed prior to the isolation of ribonolactone; and allows real-time monitoring of the reaction.    DETAILED DESCRIPTION - Preparing a ribonolactone (I) comprises reacting fructosamine compounds of formula (II) in the presence of a calcium salt in a non-aqueous reaction medium, to provide (I).    Either R1a, R2a = 1-6C alkyl, benzyl, allyl, phenyl or naphthyl (all substituted with 0-6 halo, -OH, 1-12C alkyl, -O(1-6C alkyl), -NO2, -NH2, -N(1-6C alkyl)2, -CO2H, -CO2(1-6C alkyl)2, benzyl, allyl and/or phenyl); or    NR1a+R2a = cyclic amine comprising pyrrolidine, piperidine, 1-azacycloheptane, morpholine or piperazine, where the cyclic amine is substituted with 0-6 halo, -OH, 1-12C alkyl, -O(1-6C alkyl), -NO2, -NH2, -N(1-6C alkyl)2, -CO2H, -CO2(1-6C alkyl)2, benzyl, allyl and/or phenyl.    An INDEPENDENT CLAIM is also included for preparing (3R,4R,5R)-3,4-bihydroxy-5-hydroxymethyl-3-methyl-dihydro-furan-2-one (ribonolactone stereoisomer) (Ia) comprising reacting (2R,3S,4R,5R)-2-((benzyl-methyl-amino)-methyl)-tetrahydro-pyran-2,3,4,5-tetraol (fructosamine stereoisomer) (IIa) in the presence of calcium chloride and sodium methoxide in a mixture of methanol and tetrahydrofuran, to provide (Ia).