Glycosides Isolated from Natural Products

3 Glycosides Isolated from Natural Products. - As usual in this series, only a selection of papers published on this aspect of glycoside chemistry are dealt with those describing compounds with notable biological properties or structural features. 

The leaf-closing substance 79 has been isolated from a nyctinastic plant, and compound 80 is a new lignan glycoside isolated in tiny proportions from the roots of Saussurea lappa Xyloside 81 is a new glycoside isolated from the mycelia of Hericium erinaceum which contains compounds that stimulate nerve growth factor synthesis. Two derivatives were made by chemical transformations. 

3-0-a-D-Galactopyranosyl-D-d ro-inositol is a novel product found in buckwheat seeds, and the further glycosylated inositol derivative 82 has been isolated from the roots of P. acidus as a derivative bonded to a terpene at the 

The absolute stereochemistry of oceanapiside, the antifungal compound 83 isolated from a marine sponge, has been determined.Four new cerebrosides which induce neuronal differentiation in rat PC 12 cells have been isolated from an edible Chinese mushroom and found to have structures 84-87.  

Further examples of the family of fattiviracin antiviral antibiotics with different lengths of fatty acid chains (see Vol. 32, p. 244) include compound 88. Compound 89, with R = 2,3-di-0-methyl-a-L-fucosyl-(l- 3)-2,4-dimethyl-p-D-xylose, is a powerful toxic metabolite of the red alga Polycavernosa tsudai and its total synthesis has been reported. The biosynthesis pathways to vicenistatin 1, 90 (R = 2,4,6-trideoxy-4-methylamino-p-D-riho-hexose) and vicenistatin 2, 90 

4 Synthe of Disaccharides and Their Derivatives - A review in Japanese has described convenient syntheses of di- and trisaccharide units which are involved in molecular recognition events. In the main it relates to enzymic methods. 

Enzymic methods were used to link a-D-glucopyranose to the anomeric positions of a-D-lyxopyranose and P-D-xylulose. Various dichloro-dideoxy sucroses and products derived by selective nucleophilic displacement of single chlorine atoms are referred to in Chapter 8. Trehalose derivatives carrying long-chain branched fatty acid residues are referred to in Chapter 19. 

A systematic investigation of the use of glycosyl acetates with trimethylsilyl triflate as activator in disaccharide synthesis has been conducted.  

The cationic heterocyclic aminals 45 are novel glycosylating agents. Compound 45 (R = H, X = Cl), treated with allyl 4,6-0-benzylidene-a-D-glucopyranoside, afforded 90% of the a-(l- 2)-linked kojibiose derivative. Tetra-O-benzyl-a-D- 

Immobilised glucoamylase in the presence of organic solvents can be used to produce e.g. maltose, isomaltose and panose.  

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O-Glycosides Isolated from Natural Products. — As usual, this Section is highly selective many examples with simple and complex glycosyl substituents have been reported. 

Glycosides Isolated from Natural Products.—As usual, only compounds showing special features, either structural or biological, are dealt widi in this section. 

Disregarding nonoxygen functional groups (amino, dimethylamino, and so on) only the 2,3,6-trideoxyhexoses were isolated from natural products. However, some of the isomeric trideoxyhexoses were chemically synthesized. Thus, the methyl a-glycosides of 3,4,6 - tr i de o xy - d - erj> f/ ro - he x o p y r a n o s e, 3,4,6-tri-deoxy-D-t/zreo-hexopyranose and 2,4,6-trideoxy-D-eryt/iro-hexopyranose were synthesized from methyl 4,6-dideoxy-a-D-xy/o-hexopyranoside via selective sub-... 

O-Glycosldes Isolated from Natural Products.- As usual, this section is highly selective many examples of simple and complex glycosides have been reported which contain unremarkable sugars and are here disregarded. 

GIvcosides Isolated from Natural Products.—As is usual practice, only selected papers are referred to in this section. To add to the list of D-allopiyranosides isolated from natural sources the butenyl compound (63) has been obtained from the leaves of Cardiomanes reniforme ° The vinyl glycoside (64) occurs in the leaves of G. pneumonanthe, and the similar isomeric substances potassium lespedezate and isolespedezate (65) were isolated from Lespedeza cuneata and also synthesised. ... 

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