The protection of thymine and guanine residues in oligodeoxyribonucleotide synthesis

Abstract

Thymidine is converted in four steps into its crystalline 4-O-phenyl derivative (14b) in 72% overall yield. 2′-Deoxyguanosine is converted in five steps into its 6-O-(2-nitrophenyl)-2-N-phenylacetyl and crystalline 6-O-(3,5-dichlorophenyl)-2-N-phenylacetyl derivatives [(19a) and (19b), respectively] in ca. 39 and 42% overall yields, respectively. Compounds (14b), (19a), and (19b) are converted into the corresponding crystalline 5′-O-(9-phenyl-9H-xanthen-9-yl) derivatives (15), (20a), and (20b), respectively. The actions of N¹,N¹,N³,N³-tetramethylguanidinium 2-nitrobenzaldehyde oximate, 80% acetic acid, potassium carbonate in aqueous dioxane, pyridine, and triethylammonium toluene-p-thiolate on (14b), (19a), and (19b) have been investigated.