NEW MATERIAL:A compound of formula I [R1 is alkyl or aryl; B is base residue (having a protecting group); Y is R2 or formula II (R2 and R3 are protecting group; R4 is protecting group, deoxynucleoside residue or deoxynucleotide residue)] and an amine salt thereof.

EXAMPLE: 5'-O-Triethylstannyl-3'-O-tert-butyldimethylsilylthymidine.

USE: An intermediate for producing oligonucleotides.

PREPARATION: An organotin amide compound of formula III (R5 and R6 are H, alkyl or aryl) is reacted with a deoxynucleoside of formula IV or a deoxynucleotide of formula V to afford the aimed compound of formula I .