This invention relates to a process for preparing a 3'-deoxypentopyranosyl oligomer, which includes the steps of bonding a 4'-protected-3'-deoxypentopyranosyl nucleoside to a solid support, deprotecting the nucleoside at the 4'-position, reacting the 2'OH group with a 4'-protected-3'-deoxypentopyranosyl nucleoside phosphoramidite in the presence of a coupling reagent, and oxidizing the reaction product. The steps of deprotecting the nucleoside at the 4'position, reacting the 2'OH group with a 4'-protected-3'-deoxypentopyranosyl nucleoside phosphoramidite in the presence of a coupling reagent, and oxidizing the reaction product can be repeated one or more times to produce the desired length of oligomer.