Transient protection in nucleoside synthesis using trityl groups: is it necessary to block hydroxyl groups?

Synthesis and Properties of O‐β‐D‐ribofuranosyl‐(1″→2′)‐guanosine‐5″‐ O‐phosphate and Its Derivatives

“…Our attempts to use 1,2,3-tri-O-benzoyl-d-ribofuranose and its 5-O-monomethoxytrityl derivative [16] resulted in a complex mixture with the formation of the desired disaccharide product in very low yield. The same results were obtained with 1,2,3-tri-O- [17].…”

“…For the preparation of 2, readily available in three steps from d-ribose, 1,2,3-tri-Obenzoyl-d-ribofuranose [16] was chosen as a starting compound. Anomers of 2, which may be easily separated on silica-gel column, were used for the next glycosylation step under standard conditions [9 ± 13].…”

Oligonucleotides Containing Disaccharide Nucleosides

“…The readily available triacetate 6 was chosen as the starting material [18] (Scheme). Introduction of the azide functionality consisted in sulfonylation of the primary OH group with tosyl chloride followed by replacement with azide ion [19] [20], without chromatographic separation of the intermediate 5-O-tosylated sugar.…”

Synthesis of a Bioreversibly Masked Lipophilic Adenosine Diphosphate Ribose Derivative

“…To enablet he formationo fa nomerically pure analogues, separation of the anomersw as envisaged.I ne arlier reports two chemical approaches toward the formation of compound a/b-7 were described as two-step syntheses starting from dribose (8), with am ethoxytrityl (MMTr) protecting group for the 5-O-position and acetyl protecting groups for the remaining hydroxy groups. [23][24] Because selective protection of 5 with tert-butyldimethylsilyl chloride (TBDMS-Cl) and acetic anhydride was successful, this protocol was used here instead for the formation of am ixture of a/b-9 (Scheme 2): d-ribose (8) was silylated and acetylated to give the fully protected ribose a/b-9 in ay ield of 64 %a nd an anomeric ratio of 1:1. It was possible to separate the a-a nd the b-anomers at this early step.…”