Synthesis of polynucleotides using combined oxidation/deprotection chemistry

A method of fabricating an addressable array of polynucleotides on a substrate carrying substrate bound moieties each with a hydroxyl group, comprising, at each of multiple different substrate addresses:

• (a) coupling a nucleoside to a second nucleoside through a phosphite linkage, wherein the coupled nucleoside has a non-carbonate protecting group protecting a hydroxyl;
• and
• (b) exposing the product of step (a) to a composition which both oxidizes the phosphite formed in step (a) to a phosphate and deprotects the protected hydroxyl of the coupled nucleoside;
• (c) repeating steps (a) and (b) wherein the deprotected hydroxyl of the coupled nucleoside in one cycle of the steps serves as the hydroxyl group of substrate bound moieties in the next cycle, so as to form the addressable array with different polynucleotide sequences at different addresses.