Resin glycosides

5-trihydroxy-6-methyltetrahydro-2//-pyran-2-yloxy)hexadecahydropyrano-[3,2-Z ] [1,4]dioxacyclopentadecin-3-yl)-3-hydroxy-2-niethylbutanoate. 

Cuscutic resinoside A (1 tetradecanoic acid, (115)-[[6-deoxy-3-(9-(6-deoxy-a-L-mannopyranosyl)-4-0-[(2/ ,3R)-3-hydroxy-2-niethyl-l-oxobutyl]-a-L-nianno-pyranosyl]oxy]-intramol. l,2 -ester) was obtained from the ethyl acetate-soluble fraction of a methanol extract prepared from the seeds of Cuscuta chinensis Lam. The purification of this compound employed a combination of column and preparative-scale HPLC. The structure was deduced from spectroscopic evidence and acid hydrolysis 14). The degradative process gave convolvuUnolic acid, nilic acid, and L-rhamnose. The sugar components were identified by GC analysis after being converted to their thiazolidine derivatives. This disaccharide has a unique macrocyclic lactone, which is placed between C-1 and C-2 of the first rhamnose moiety. 

Two trisaccharide macrolactones have been characterized from the aerial parts of Ipomoea tricolor Cav. (syn. Ipomoea violacea L.) (heavenly blue), namely, tricolorins 

Cuscutic acids A (tetradecanoic acid, (115)-[(0-6-deoxy-a-L-mannopyranosyl-(l- 3)-(9-6-deoxy-a-L-mannopyranosyl-(1 2)-0-/l-D-glucopyranosyl-(1 2)-)S- 

Ipomoea operculata has afforded three resin glycosides containing this glyco-sidic acid, operculins VI (19), XI (20), and XII (21). The macrolactone site was located at C-2 of the first rhamnose unit for 19 while in compounds 20 and 21 the lactonization was placed at C-3, the same site for mammosides A (17) and B (18). Two dodecanoyl residues are the fatty acids present in these resin glycosides and located at C-2 of the second rhamnose and at C-4 of the third rhamnose for operculin VI (19). For operculins XI (20) and XII (21), they were placed at C-2 or C-3 of the second rhamnose and C-4 at the third rhamnose (27). 

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Scheme 45 Macrocyclization by RCM in Fiirstner s total synthesis of the resin glycoside woodrosin I (218) [104]...

The synthesis of the disaccharide subunit 85 of tricolorin A, a cytotoxic resin glycoside isolated from lpomoea tricolor, provides a unique opportunity to compare the efficiency of an RCM-based macro cyclization reaction with that of a more conventional macrolactonization strategy. Furthermore, this specific target molecule challenges the compatibility of the catalysts with various functional groups. 

Resin Glycosides from the Morning Glory Family... 

Operculinic acids E (hexadecanoic acid, (115)-[(0-6-deoxy-a-L-mannopyranosyl-(1 4)-0-6-deoxy-a-L-mannopyranosyl-(1 4)-0-6-deoxy-a-L-mannopyranosyl-(1 2)-jS-D-glucopyranosyl)oxy]) and F (hexadecanoic acid, (115)-[(0-6-deoxy-a-L-mannopyranosyl-(1 4)-0-6-deoxy-a-L-mannopyranosyl-(1 4)-0-6-deoxy-a-L-mannopyranosyl-(1 2)-/i-D-xylopyranosyl)oxy]) were obtained by alkaline hydrolysis of the ether-soluble crude resin glycosides from the roots of Ipomoea... 

The methyl ester of operculinic acid E was obtained by basic hydrolysis and methylation of the crude resin glycoside mixture of 7. murucoides. Mumcoidins XII (53) and XIII (54) afford operculinic acid E as their oligosaccharide core. The lactonization site was placed at C-3 of the first rhamnose unit. These resin glycosides contain an esterifying residue that is composed of n-dodecanoic or (25)-methylbu-tyric acids at the C-2 or C-3 positions on the second rhamnose unit of the oligosaccharide core and (25)-methylbutyric acid at C-4 on the third rhamnose (30). 

Scammonin VII (62), as a minor ether-soluble resin glycoside, was isolated by reversed-phase HPLC from Convulvulus scammonia L. (47). Under basic hydrolysis, it gave orizabic acid A as weU as 2-methyIbutyric and tiglic acids. Compound 62 exhibits lactonization at C-3 of the rhamnose unit and is acylated by a (25)-methylbutanoyl residue at C-2 of the rhairmose unit and a tigloyl residue at C-4 of the terminal quinovose. 

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