PURPOSE: To simply obtain the subject compd. useful as a synthetic intermediate of an antiviral agent and an AIDS treatment agent by condensing two kinds of specific compds. in the presence of an inert solvent.

CONSTITUTION: 2-Amino-β-D-arabinofurano[1',2':4,5]oxazoline represented by formula I (wherein R3 is H, triphenylmethyl or silyl and substituted by three substituents selected consisting of a 1-6 alkyl, phenyl and a combination of them) and a compd. represented by formula II [wherein R1 is a 1-4C alkyl, X is a halogen or OR2 (R2 is H, a 1-4C alkyl or phenyl)] are reacted at 0-150°C, pref., at 20-80°C in an inert solvent (pref., methanol) to obtain the objective compd. represented by formula III.