The aim of the present work is the synthesis of new carbohydrate derivatives containing 1,2,4-triazole or 1,3,4-oxadiazole from D-galactose as shown in scheme [A]. To obtain these derivatives, the diacetone galctose (5) was chosen as the starting material, which was obtained from the reaction of anhydrous galactose with dry acetone in presence of zinc chloride. Oxidation of (5) with potassium permanganate in potassium hydroxide solution gave the acid (8). Esterification of the acid with dimethyl sulphate gave the methyl ester (66). Treatment of the methyl ester (66) with hydrazine hydrate gave the hydrazide (67), which is the desired chiron. The hydrazide (67) was used for the preparation of four types of heterocyclic derivatives:- 1. l,2,4-Triazole-5-thiol(69,70a-d). 2. l,2,4-Triazole-5-.ol (72,73a-d). 3. 4-Amino-1,2,4-Oxadiazole-2-thiol (77,78a-d). (1)The compound 3-(l',2':3',4'-di-O-isopropylidene-a-L-arabino- pyrannos-5'-yl)-4- phenyl-l,2,4-triazole-5-tliioi (69) was syinthesized by the intramolecular cyclization of the thiosemicarbozide derivative (68), which was obtained from the reaction between the hydrazide (67) and phenylisothiocyanate. Alkylation of (69) with different alkyl halides give (70a-d). (2) 3-( 1 ',2':3 ',4'-Di-O-isopropylidene-a-L-arabinopyrannos-5'-yl)- 4- phenyl-1,2,4-triazole-5-ol (72) was synthesized in a similar manner that used for preparation of (69). , (3) 3-(l',2':3',4'-Di-O-isopropylidene-a-Larabinopyrannos- 5'-yl)-4-amino-5-mercapto-1,2,4-triazole (75) was obtained from cyclization of xanthate salt (74) using hydrazine hydrate. The triazole (75) was then reacted with different aromatic aldehydes which gave the corresponding Schiff-base (76ai). (4) 5-(l',2':3',4'-Di-O-isopropylidene-a-L-arabinopyrannos-5'-yl)-l,3,4-oxadiazole-2- thiol (77) was prepared from the reaction of the hydrazide (67) with carbon disulfide in the presence of KOH. Alkylation of the thio-oxadizole (77) using different alkyl halides give the alkyl thio-ether oxadiazole derivatives (78a-d). All the synthesized compounds were characterized by all or some of the following techniques: CHN analysis, IR, ¹HNMR, I3CNMR, Two dimensional ¹H-I3CNMR and Mass spectroscopy.