Cover Feature: Black Swan in Phase Transfer Catalysis: Influence of Mixing Mode on the Stereoselectivity of Glycosylation (Eur. J. Org. Chem. 14/2022)

Abstract

The Cover Feature allegorizes differently arranged long‐lived supramolecular structures (supramers), formed from reagent molecules in the reaction solution, as different groups of dancers holding hands. The supramer hypothesis has been invoked to rationally discuss the experimentally observed change in reaction mechanism induced by the change in mixing mode. Cover design by Maria Panova. More information can be found in the Research Article by L. O. Kononov et al.

Enabling Technologies in Carbohydrate Chemistry: Automated Glycan Assembly, Flow Chemistry and Data Science

“…This glycosyl donor was reported to give unreliable or mediocre yields and stereoselectivity, an observation that was initially attributed to its inherent reactivity, [22] or the formation of supramers. [23] Fukase Scheme 1. Orthogonal mannoside phosphate 1 enables the synthesis of highly branched glycan precursors 1 a and 1 b.…”

“…The glycosylations involving the modified C5‐trichloroacetamide sialic acid 2 are one example of such cases. This glycosyl donor was reported to give unreliable or mediocre yields and stereoselectivity, an observation that was initially attributed to its inherent reactivity, [22] or the formation of supramers [23] . Fukase and co‐workers, however, hypothesized poor mixing and lack of precise temperature control in the activator addition as reasons for the poor performance of this donor in conventional batch reactions [24] .…”

“…The adoption of flow chemistry in glycan synthesis is still limited, despite several reports highlighting the potential advantages of microreactors. Concerning glycosylations, microreactors have been used as a screening platform, [18,28,29] for mechanistic studies [23] or to tackle challenging glycosidic linkages such as β‐mannosylation [25] and α‐sialylation [24] . For the synthesis of glycan precursors, flow chemistry has mostly been used to address scale‐up [17] or safety issues [31] …”