Site-Divergent Delivery of Terminal Propargyls to Carbohydrates by Synergistic Catalysis

Abstract

The direct, selective modification of carbohydrates represents a significant challenge in chemistry. Here, we show that synergistic catalysis, a strategy that combines the catalytic effects of two distinct catalysts, could be a powerful tool for addressing the site-selectivity issue during the modification of monosaccharides. By exploiting a borinic acid and a copper catalyst simultaneously, this method enables delivery of valuable terminal propargyl groups to various monosaccharides and natural products in a mild, direct, and site-divergent manner.

Scope and advances in the catalytic propargylic substitution reaction

“…98 A similar report of copper and borinic acid-catalyzed propargylic etherication reactions was also independently carried out by the group of Niu in 2017. 117,118 But the substrate scope is limited and has been limited to diols and polyols, which may coordinate the boron center in a bidentate fashion.…”

Site-switchable mono-O-allylation of polyols

“…In this realm, various methods 21,22 have been established to selectively modify the intrinsically most reactive hydroxyl groups within a substrate (substrate control). Recently, systems that can override the intrinsic reactivity preferences and accomplish catalyst-controlled, site-switchable modification of complex polyols have emerged [23][24][25][26][27][28][29][30][31][32][33][34][35] . As eminent examples, in a series of landmark studies, the Miller group [23][24][25][26] , has identified several oligopeptide-based catalysts that enabled site-switchable modification of complex antibiotics, such as vancomycin, teicoplanin, and erythromycin.…”

Chiral Benzazaborole‐Catalyzed Regioselective Sulfonylation of Unprotected Carbohydrate Derivatives

“…[12,13] However,t ot he best of our knowledge,a general method, which uses organoborons for the regioselec-tive functionalization of unprotectedc arbohydrates has not been reported. [14][15][16] This is because the organoboronc atalyst binds to both cis-1,2-diol and 1,3-diolm oieties (Scheme 1e). [12,14] Herein, we describe the chiral benzazaborole-catalyzed regioselective sulfonylation of unprotected carbohydrates.…”

“…[14][15][16] This is because the organoboronc atalyst binds to both cis-1,2-diol and 1,3-diolm oieties (Scheme 1e). [12,14] Herein, we describe the chiral benzazaborole-catalyzed regioselective sulfonylation of unprotected carbohydrates. [17] Sulfonylated carbohydrates are used as electrophilesi nt he synthesis of biologically interesting pseudosugars and buildingb locks.…”

“…To our delight, the use of the chiral benzazaborole 1f was effective for the regioselective sulfonylation with assistance of NMI, [20] and product 3a was predominantly furnished in 71 %y ield ( Table 1, entry 6). [21] The high catalytic activity of 1f would be derived by the electrond onation from the nitrogen atom ontot he boron center.I ntroduction of am ethoxy substituent on the quinoline ring did not improvet he chemical yield ( [10][11][12][13][14]. Among the tested solvents, acetonitrile gave the best result( Ta ble 1, entries [15][16][17][18][19].…”