5019-22-7Relevant articles and documents
General Strategy for the Synthesis of Rare Sugars via Ru(II)-Catalyzed and Boron-Mediated Selective Epimerization of 1,2- trans-Diols to 1,2- cis-Diols
Li, Xiaolei,Tang, Weiping,Wu, Jicheng
, p. 3727 - 3736 (2022/03/02)
Human glycans are primarily composed of nine common sugar building blocks. On the other hand, several hundred monosaccharides have been discovered in bacteria and most of them are not readily available. The ability to access these rare sugars and the corresponding glycoconjugates can facilitate the studies of various fundamentally important biological processes in bacteria, including interactions between microbiota and the human host. Many rare sugars also exist in a variety of natural products and pharmaceutical reagents with significant biological activities. Although several methods have been developed for the synthesis of rare monosaccharides, most of them involve lengthy steps. Herein, we report an efficient and general strategy that can provide access to rare sugars from commercially available common monosaccharides via a one-step Ru(II)-catalyzed and boron-mediated selective epimerization of 1,2-trans-diols to 1,2-cis-diols. The formation of boronate esters drives the equilibrium toward 1,2-cis-diol products, which can be immediately used for further selective functionalization and glycosylation. The utility of this strategy was demonstrated by the efficient construction of glycoside skeletons in natural products or bioactive compounds.
Structural properties of D-mannopyranosyl rings containing O-Acetyl side-chains
Turney, Toby,Zhang, Wenhui,Oliver, Allen G.,Serianni, Anthony S.
, p. 1166 - 1174 (2019/08/13)
The crystal structures of 1,2,3,4,6-penta-O-Acetyl--d-mannopyranose, C16H22O11, and 2,3,4,6-Tetra-O-Acetyl--d-mannopyranosyl-(1.2)-3,4,6-Tri-O-Acetyl--d-mannopyranosyl-( 1.3)-1,2,4,6-Tetra-O-Acetyl--d-mannopyranose, C40H54O27, were determined and compared to those of methyl 2,3,4,6-Tetra-O-Acetyl--d-mannopyranoside, methyl -d-mannopyranoside andmethyl -d-mannopyranosyl-(1.2)--d-mannopyranoside to evaluate the effects of O-Acetylation on bond lengths, bond angles and torsion angles. In general, O-Acetylation exerts little effect on the exo-and endocyclic C-C and endocyclic C-O bond lengths, but the exocyclic C-O bonds involved in O-Acetylation are lengthened by -0.02 A ° . The conformation of the O-Acetyl side-chains is highly conserved, with the carbonyl O atom either eclipsing the H atom attached to a 2-Alcoholic C atom or bisecting the H-C-H bond angle of a 1-Alcoholic C atom. Of the two C-O bonds that determine O-Acetyl side-chain conformation, that involving the alcoholic C atom exhibits greater rotational variability than that involving the carbonyl C atom. These findings are in good agreement with recent solution NMR studies of O-Acetyl side-chain conformations in saccharides. Experimental evidence was also obtained to confirm density functional theory (DFT) predictions of C-O and O-H bond-length behavior in a C-O-H fragment involved in hydrogen bonding.
One-pot oxidation-hydrocyanation sequence coupled to lipase-catalyzed diastereoresolution in the chemoenzymatic synthesis of sugar cyanohydrin esters
Hietanen, Ari,Kanerva, Liisa T.
experimental part, p. 2729 - 2737 (2012/07/13)
A three-step, one-pot synthesis and diastereoresolution sequence is described in anhydrous toluene starting from methyl α-D-2,3,4-tri-O- acetylgalacto- (1a), -manno- (1b) and -glucopyranosides (1c). The reaction sequence, including consecutive transformations through the aldehyde [PhI(OAc)2, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)] and cyanohydrin [basic resin or (R)-oxynitrilase] into the (6R)-cyanohydrin ester (lipase) is shown to proceed in a one-pot cascade, except that the basic resin (when used) should be removed before the addition of the enzymatic acylation reagents. We have shown that the effective transformation of 1a (75 % reaction yield) through labile intermediates gives the stable (6R)-cyanohydrin butanoate (85 % de). Further diastereomeric purification by chromatography is possible, although the product is already of high diastereopurity. (6R)-Cyanohydrin esters are obtained through acylation with Burkholderia cepacia lipase. The (6S)-ester (de 99 %) is produced by Candida rugosa lipase when the sequence is started from 1c whereas the other sugar derivatives are less suited to the reaction with lipase. Copyright
