Glycoside preparation

POMCl, (/-Pr)2NEt, CH2Cl2. The related pentenyl glycosides, prepared by the usual methods, were used to protect the anomeric center. ... 

Formyl C-glycosides, prepared in three steps via the thiazole-based formy-lation of sugar lactones are readily condensed with hydroxylamine to give the corresponding oximes. The latter are the precursors of glycosyl nitrile oxides via the N-bromosuccinimide method (41). 

The primary aim of this chapter is to demonstrate different strategies, chemical and chemo-enzymatic, for the preparation of glycosides of pharmaceutically active and broadly used compounds - ergot alkaloids. New glycosides prepared recently have interesting immunomodulatory, neuroactive and cytostatic activity. 

McDevitt, R E, Fraser-Reid, B, A divergent route for a total synthesis of cyclophellitol and epicyclophellitol from a [2.2.2]oxabicyclic glycoside prepared from D-glucal, J. Org. Chem., 59, 3250-3252, 1994. 

Two natural product derived semisynthetic compounds are utilized as a limited basis, namely, perillartine [28] and neohesperidin dihydrochalcone [45]. Perillartine is an a-jy -oxime and synthesized from perillaldehyde, a constituent of the volatile oil of Perilla frutescens (L.) Britton (Labiatae), and used in Japan as a sweetener for tobacco [28]. Neohesperidin dihydrochalcone is a dihydrochalcone glycoside prepared from a flavanone constituent of Citrus aurantium L. (Rutaceae), which is permitted for use in chewing gum and certain beverages in Belgium and elsewhere [45]. 

Although alkaloids are mostly produced by plants where glycosylation occurs quite often there are only a few examples of natural alkaloid glycosides, and their biological activities have not been studied to a large extent. There are, however, many examples of alkaloid glycosides prepared artificially for a specific (pharmacological) reason. 

As it was already mentioned above, glycosides from Cucumaria japonica demonstrate a restorative effect in mice with acquired immunodeficiency induced by radiation [102]. Individual triterpene glycoside cucumarioside A2-2 (18) from C. japonica and glycoside preparation trepangin from the Far Eastern sea cucumber Apostichopus japonicus showed radioprotective properties while cucumarioside A2-2 was significantly more active in this respect. Survival of lethally radiated mice (y-rays, Cs at 7.7 GR, 5-10 min) after glycoside 18 administration at the dose of 1 pg/kg was about 40 % over control and after 60 min radiation was about 20 %. The restoration of hemopoesis was observed in the radiated glycoside-dosed animals [108]. 

Kahne glycosidation Preparation of 0-, S- or A/-glycosides via the activation of glycosyl sulfoxides. 234... 

The cardiac glycoside preparations that have been used range from powdered digitalis leaf to... 

All cardiac glycosides preparations have the potential to cause toxicity. Because the minimal toxic dose of the glycosides is only two- to threefold the therapeutic dose, intoxication is quite common. In mild to moderate toxicity, the common symptoms are anorexia, nausea and vomiting, muscular weakness, bradycardia, and ventricular premature contractions. The nausea is a result of excitation of the chemoreceptor trigger zone in the medulla. In severe toxicity, the common symptoms are blurred vision, disorientation, diarrhea, ventricular tachycardia, and AV block, which may progress into ventricular fibrillation. It generally is accepted that the toxicity of the cardiac glycosides results from inhibition of the Na /K -ATPase pump, which results in increased intracellular levels of Ca ". Hypokalemia (decreased potassium), which can be induced by coadministration of... 

Glycoside preparations are also used to correct atrial fibrillation and atrial flutter (cardiac dysrhythmia). 

---