Super arming of a glycosyl donor using a molecular lever

Conformationally Switchable Glycosyl Donors

“…Based on the above observations, superarmed glycosyl donors were introduced. , Equatorial hydroxyl groups are protected with bulky silyl protective groups, inducing a ring-flip, which increases the reactivity by 3 orders of magnitude . A similar increase in reactivity is also achievable by other means, e.g., 3,6- O -tethering , and molecular levers . In this work, a molecular conformational switch, which can induce a ring-flip, is presented.…”

“…8 A similar increase in reactivity is also achievable by other means, e.g., 3,6-Otethering 9,10 and molecular levers. 11 In this work, a molecular conformational switch, which can induce a ring-flip, is presented. Conformational switches are molecules that can reversibly change between two or more conformational states under external influence.…”

Conformationally Constrained Glycosyl Donors as Tools to Control Glycosylation Outcomes

“…The concept of a “molecular lever” created via the use of a 2,3-(phenyl-1,2-ethylidine) tethering group was introduced in 2016 by the Bols group (Scheme ). The group demonstrated that due to 1,3-diaxial interactions when the phenyl group is in an axial position, glycosyl donors 225 and 226 were forced to adopt an unfavorable but highly reactive 1 C 4 conformation where the phenyl group is in an equatorial position. This is not the case for 227 (epimer of 225 where the phenyl substituent has the opposite stereochemistry), since in this case, the unfavorable 1,3-diaxial interactions disfavor the 1 C 4 conformation.…”

“…However, perhaps somewhat surprisingly based on previous work, this chelation-driven conformational switch did not have a dramatic impact upon the reactivity or the anomeric selectivity of the chelated glycosyl donor, with only a slightly higher preference for the αanomer observed for axial-rich chelated donor 224. duced in 2016 by the Bols group (Scheme 35). 147 The group demonstrated that due to 1,3-diaxial interactions when the phenyl group is in an axial position, glycosyl donors 225 and 226 were forced to adopt an unfavorable but highly reactive 3. GLYCOSYLATIONS USING ANOMERICALLY TETHERED GLYCOSYL DONORS In 2000, Oscarson and Sehgelmeble introduced a new concept for controlling the stereochemical outcome of glycosylation reactions by using an anomeric tether.…”

Conformational Distortion Using a Molecular Lever: Synthesis and Conformational Studies of Galactoside Derivatives

“…Inspired by the low ring‐inversion barrier in cis decalin,, we recently demonstrated that d ‐mannopyranosides containing a 2,3‐(phenyl‐1,2‐ethylidene) protective group, changes conformation dependent on the stereochemistry of the external ring (see Figure ) . The phenyl group, in the external ring, acts as a molecular lever, which due to its bulk resides equatorially.…”