and washed with dry pyridine msnt 1 5 mg 10 u03bcmol in pyridine 200 u03bcl was added the reaction proceeded at room temperature for 3 hr with occasional shaking after centrifugation the liquid phase was removed and the support was washed with acetonitrile 3 u00d7 1 0 ml d oligonucleotide deprotection and release of the free 3 u2032 hydroxyl fig6 the washed support was treated with tetrabutylammonium fluoride tbaf 0 5 m 200 u03bcl for 2 hr at room temperature although tbaf is sufficient to cleave the disiloxyl bridge 2 chlorophenyl ester bond and 2 cyanoethyl phosphotriester bonds the support was further treated with conc aqueous ammonia to resemble standard oligonucleotide deprotection conditions additionally a treatment with 4 nitrobenzaloxime and tetramethylguanidine may be introduced prior to fluoride treatment to reverse possible side reactions caused by msnt the mixed liquid phase after fluoride ammonia treatment was isolated and the solid support was washed with water 3 u00d7 0 5 ml the combined extracts were evaporated desalted on a nap 10 column pharmacia biotech ab and analyzed on a hplc system hitachi merck la chrom using a lichrospher rp 18 5 mm merck and linear gradient of solvent a acetonitrile 5 v v in triethylammonium acetate 0 1 m ph 7 and solvent b acetonitrile 40 v v in triethylammonium acetate 0 1 m ph 7 this analysis revealed the presence of cleaved non inverted oligonucleotides accompanied by a side product 5 u2032.