Protecting Groups at the Primary Position of Carbohydrates

Synthesis of carbohydrate building blocksviaregioselective uniform protection/deprotection strategies

“…Primary hydroxyl groups are sterically less hindered than their secondary counterparts, which offers an opportunity for their regioselective protection. 17 The best-known examples is the use of bulky (trityl, silyl) protecting groups to selectively protect primary hydroxyl groups in the presence of secondary ones. Steric hindrance, as well as the electronic effects, can also be utilized to some extent to discriminate between certain secondary hydroxyl groups.…”

Selective Acetylation of Non-anomeric Groups of per-O-Trimethylsilylated Sugars

“…6 Because of their ease of preparation and good stability, per-acetylated sugars are commonly used as precursors for such kinds of adjustments. 7 The majority of peracetylation reactions are carried out using excess acetic anhydride (Ac 2 O) as an acetylating agent in the presence of pyridine 8 or its derivatives like 4-(dimethylamino)pyridine 9,10 as catalysts, though plenty of other protocols are also available. 11 In order to address the issue of regioselectivity in acetylations, a number of attempts have been made over the past several years involving reactions by both chemical 12−16 and enzymatic 17,18 methods.…”

“…Thus, our methodology can remarkably speed up chemical glycosylation in conjunction with other proven strategies such as orthogonal protection. 7,57 ■ EXPERIMENTAL SECTION General All reagents obtained from commercial sources were used without further purification. All reactions were carried out under a nitrogen atmosphere and in flame-dried glassware.…”

“…In this case, if the building block of interest is a glycosyl donor, the anomeric center should be equipped with a leaving group, whereas, if an acceptor is needed for glycosylations other than 1,1′-glycosidic linkage formation, the anomeric hydroxyl moiety should be masked with a protecting group compatible with ensuing reaction conditions . Because of their ease of preparation and good stability, per-acetylated sugars are commonly used as precursors for such kinds of adjustments . The majority of per-acetylation reactions are carried out using excess acetic anhydride (Ac 2 O) as an acetylating agent in the presence of pyridine or its derivatives like 4-(dimethylamino)­pyridine , as catalysts, though plenty of other protocols are also available .…”

“…In conclusion, we have developed an expeditious protocol that enables accessing a versatile class of sugar precursors which can significantly abate the main bottleneck of carbohydrate synthesis: notably prolonged reaction time due to the protection-deprotection manipulation of protecting groups. Thus, our methodology can remarkably speed up chemical glycosylation in conjunction with other proven strategies such as orthogonal protection. , …”