Synthesis of KDO and analogues from a novel mannose-derived precursor

Recent advances on synthesis of C-glycosides

In recent years, C-glycosides have emerged as significant building blocks for many naturally occurring alkaloids and pharmaceutically active drug molecules. Therefore, significant efforts have been devoted to the construction of structurally important C-glycosidic linkages in carbohydrate compounds. Herein, we have summarized the recent developments of diverse synthesis of C-glycoside core between the time period from 2019 to 2022 focusing on different catalytic strategies, such as (i) transition-metal, and (ii) metal-free catalytic approaches. Further, the transition metal catalyzed C-glycosylations have been categorized into four sub classes: (a) metal based C-H activation, (b) cross-coupling reaction, (c) glycosyl radical intermediate-based process, and (d) Others.

Stereoselective Synthesis of β-C-Glycosides of 3-Deoxy-d-manno-oct-2-ulosonic Acid (Kdo) via SmI2-Mediated Reformatsky Reactions

An efficient and simple approach for stereoselective synthesis of β-Kdo C-glycosides was described, which relies on easily available peracetylated anomeric acetate or anomeric 2-pyridyl sulfide to couple with carbonyl compounds via SmI₂-mediated Reformatsky reactions. The utility of this methodology is exemplified by the streamlined synthesis of a practical β-Kdo C-glycoside with an anomeric aminopropyl linker to conjugate with other biomolecules for further biological studies.

C-Glycopyranosyl Arenes and Hetarenes: Synthetic Methods and Bioactivity Focused on Antidiabetic Potential

This Review summarizes close to 500 primary publications and surveys published since 2000 about the syntheses and diverse bioactivities of C-glycopyranosyl (het)arenes. A classification of the preparative routes to these synthetic targets according to methodologies and compound categories is provided. Several of these compounds, regardless of their natural or synthetic origin, display antidiabetic properties due to enzyme inhibition (glycogen phosphorylase, protein tyrosine phosphatase 1B) or by inhibiting renal sodium-dependent glucose cotransporter 2 (SGLT2). The latter class of synthetic inhibitors, very recently approved as antihyperglycemic drugs, opens new perspectives in the pharmacological treatment of type 2 diabetes. Various compounds with the C-glycopyranosyl (het)arene motif were subjected to biological studies displaying among others antioxidant, antiviral, antibiotic, antiadhesive, cytotoxic, and glycoenzyme inhibitory effects.

The sugar 3-deoxy-d-manno-oct-2-ulosonic acid (Kdo) as a characteristic component of bacterial endotoxin — a review of its biosynthesis, function, and placement in the lipopolysaccharide core

The sugar 3-deoxy-d-manno-oct-2-ulosonic acid (Kdo) is a characteristic component of bacterial lipopolysaccharide (LPS, endotoxin). It connects the carbohydrate part of LPS with C6 of glucosamine or 2,3-diaminoglucose of lipid A by acid-labile α-ketosidic linkage. The number of Kdo units present in LPS, the way they are connected, and the occurrence of other substituents (P, PEtn, PPEtn, Gal, or β-l-Ara4N) account for structural diversity of the inner core region of endotoxin. In a majority of cases, Kdo is crucial to the viability and growth of bacterial cells. In this paper, the biosynthesis of Kdo and the mechanism of its incorporation into the LPS structure, as well as the location of this unique component in the endotoxin core structures, have been described.

An In-Depth Study on Ring-Closing Metathesis of Carbohydrate-Derived α-Alkoxyacrylates: Efficient Syntheses of DAH, KDO, and 2-Deoxy-β-KDO

Novel, efficient synthetic pathways to DAH, KDO, and 2-deoxy-beta-KDO are described. Ring-closing metathesis (RCM) of highly functionalized alpha-alkoxyacrylate fragments resulted in a series of synthetically versatile oxygen heterocyclic intermediates. Further functionalization of the resulting enol ether double bond and subsequent deprotection provided the natural products in high overall yields, starting from commercially available protected sugars.

Synthesis of the Sialic Acid (−)-KDN and Certain Epimers from (−)-3-Dehydroshikimic Acid or (−)-Quinic Acid

(-)-3-Dehydroshikimic acid (3-DHS, 4), a C(7)-building block now available in large quantity from corn syrup, has been converted into the sialic acid (-)-KDN (3) as well as its C-7- and C-8-epimers. (-)-Quinic acid can be used for the same purpose. [structure: see text]

Purification of saponin compounds in Bupleurum falcatum by solvent partitioning and preparative LC

Saponin compounds (saikosaponin c, a, and d) in Bupleurum falcatum were partially purified by solvent partitioning of the herbal extract using diethyl ether, distilled water, n-butanol, and acetone. After separation of the saponins by preparative LC, the purity of each saikosaponin was more than 94%. The identities of purified individual saikosaponins were confirmed by TLC, analytical LC, and fast-atom bombardment mass spectrometry.