NEW MATERIAL:A compound expressed by formula I [X1 and X2 are both halogen or either one thereof is H and other is halogen; R1 is protecting group of OH; Y is O, NZ (Z is OH which may be protected) or formula II (A is H or amine residue)].

EXAMPLE: (1S)-( 1(OH)2,4/1,3 )-2,3,4-Tri-O-benzyl-1-C-(benzyloxymethyl)-6,6-dichlo ro-5-oxo-1,2,3,4-cyclohexanetetrol.

USE: A raw material for producing valiolamine having strong α-glucosidase inhibiting activity and useful as a remedy for human or animal hyperglycemia and various kind of diseases originated thereby.

PREPARATION: A D-glucono-1,5-lactone derivative expressed by formula III is reacted with dihalomethyllithium to provide a compound expressed by formula IV, which is successively subjected to ring closure of pyranose ring, oxidation of hydroxyl group in 1-position and 5-position and treatment by a base to afford the compound expressed by formula I (Y is 0).