Other Natural Glycosides

Plant Chemistry Division, Department of Scientific and Industrial Research, Palmerston North, New Zealand 

Department of Chemistry, Royal Holloway College, University of London, Englefield Green, Surrey, England 

Since the last review in this Series on the subject of oligosaccharides as such, a vast amount of literature on its various aspects has been published, and many new compounds have been isolated. The aim of the present article is to consider one aspect of oligosaccharide chemistry, the determination of structure, and to provide up-to-date Tables of the oligosaccharides which have been isolated and characterized. As a comprehensive account of all of the methods used for structural analysis is obviously impossible in the space available, the authors have concentrated on those methods, developed in the past ten years, which require only small amounts of oligosaccharide. 

Following the introduction of paper-chromatographic techniques, some fifteen years ago, there has been a steady change in the methods used for determining oligosaccharide structure. Many compounds are now only 

---

Several other naturally occurring antioxidants have been identified in oils. Sesamol [533-31-3] (6) occurs as sesamoline [526-07-8], a glycoside, in sesame seed oil. FemUc acid [1135-24-6] (7) is found esterified to cycloartenol [469-38-5] in rice bran oil and to 3-sitosterol in com oil. Although it does not occur in oils, rosemary extract has also been found to contain powerful phenoHc antioxidants (12). 

Stereoselective inverse-demand hetero (4 + 2) cycloadditions. A Chiral Template for C-Aryl Glycoside Synthesis. Chiral allenamides2 4 had been used in highly stereoselective inverse-demand hetero (4 + 2) cycloaddition reactions with heterodienes.5 These reactions lead to stereoselective synthesis of highly functionalized pyranyl heterocycles. Further elaboration of these cycloadducts provides a unique entry to C-aryl-glycosides and pyranyl structures that are common in other natural products (Scheme 1). 

The structure-sweetness relationships of other naturally occurring, sweet glycosides have received very little attention. In most cases, virtually no systematic, structural modifications have been reported. 

The occurrence of sulfated nucleoside glycosides in spider venoms, or for that matter in any other natural source, does not seem to have been previously noted. We look forward to the possibility that this novel... 

The reported procedure for the selective oxidation of natural glycosides is mild, convenient and easily reproducible. The biotransformations are performed in mildly acidic water solutions therefore, this method is complementary to other chemical approaches for the in situ regeneration of the oxidized form of TEMPO, such as sodium hypochlorite, that require alkaline pH. 

Toxicity. Atractyloside, a diterpenoid glycoside that occurs naturally in plants, may be present at levels as high as 600 mg/kg of dried plant material. Gonsumption of plants containing atractyloside or carboxyatractyl-oside has caused fatal renal proximal tubule necrosis and/or centrilobular hepatic necrosis in man and farm animals. Although pure atractyloside and crude plant extracts disrupt carbohydrate homeostasis and induce similar pathophysiological lesions in the kidney and liver, it is also possible that the toxicity of atractyloside may be confounded by the presence of other natural constituents in plants. Atractyloside competitively inhibits the adenine nucleoside... 

Anthocyanins. Like the flavones. the anthocyanins are found throughout nature. This class uf polyphenolic compounds is responsible for the pink, red. violet, and blue colors found in plants. Like many other natural phenulic substances, anthocyanins occur in plants as glycosides the sugar-free anthocyanins are known as anihocyanidins. 

Besides picrocrocin, at least one other naturally occurring glycoside would be expected to demonstrate the alkali-sensitivity of this class. Jarvis and Johnson63 have described a glycoside (LXXXIV), produced by... 

Other naturally occurring glycosidic bonds have been reviewed from Hayes and Hart as putative motif of novel libraries [28],... 

In the same way that the toxic properties of the constituents of the yew tree have encouraged investigation of all its parts, practically all Taxus species have also been studied T. baccata L. in Europe, T. brevifolia in North America, T. cuspidata, T. wallichiana, and T. mairei in Asia, and Austrotaxus spiccata Compton in New Caledonia. Although taxanes may be considered as the typical constituents of the genus Taxus, other natural products, such as ecdysones, triterpenoids, lignans, glycosides, and flavonoids have also been identified [these are described in a recent review by Ud-Din Khan and N. Parveen (75)]. 

---