Synthesis of methyl a-D-tetronitroside(Q) f rom D-mannose via methyl a-D-mycaroside(k) established the D-configuration for tetronitrose(=kijanose), a novel nitro sugar which occurs as a component of the antitumor antibiotics tetrocarcins A and B, and kijanimicin. Tetronitrose(or kijanose) is an unusual methyl-branched nitro sugar recently discovered as one of the sugar components of antitumor antibiotics tetrocarcins A and B,' and kijanimicin' respectively. Although its structure was definitely determined by X-ray crystallography' to be 2,3,4,6-tetradeoxy-4-(methoxycarbonylamino)-3-C-methyl-3-nitro-~Zo-hexopyranose and D-configuration was assigned by application of Hudson's rule of isorotation,' confirmation of the proposed absolute configuration by the synthesis has been a subject of our interest in this field. Herein we describe the synthesis of the methyl glycoside of this natural sugar from D-mannose via D-mycarose which led to conclusive proof of the proposed D-configuration. Methyl a-D-mycaroside($), mp 55.5-56.5"C, [al, +138"(CHCl,), prepared from D-mannose via 4-0_benzoyl-2,6-dideoxy-3-C-methyl-cr-D-ribo-hexopyranoside(~),3 was reacted with N,N'-thiocarbo-