.beta.-D-Allopyranoside, (3aS,4R,5R,6S,6aS)-2-(dimethylamino)-3a,5,6,6a-tetrahydro-6-hydroxy-4-(phenylmethoxy)methyl-4H-cyclopentoxazol-5-yl 2-(acetylamino)-4-O-2-(acetylamino)-2-deoxy-3-O-(phenylmethyl)-4,6-O-(phenylmethylene)-.beta.-D-allopyranosyl-2-de