Glycosylated cardenolides. VI. Ribosides of strophanthidin and digitoxigenin
Partial syntheses of ribosides of strophanthidin (I) and digitoxigenin (II) have been carried out by the orthoester method [i] by analogy with previous work [2]. 3,4-Di-O-acetyl~-D-ribopyranose 1,2-(methyl orthoacetate) (III) was obtained by the method of Mazurek and Perlin [3]. The orthoester (III), Cz2H~,Os, had mp 82-84°C (from diethyl ether--petroleum ether), [~]~4 --7.7 _+ 2 ° (c 1.78; chloroform). NMR spectrum (CDCI3), ppm: 1.75 (3 H at CH3, s), 2.10 (6 H at 2 Ac, s), 3.28 (3 H at OCH~, s). The NMR spectrum shows the exo position of the OCH3 group in compound (III) [3, 4].
SYNTHESIS OF β-D-MANNOSE 1,2-ORTHOACETATES
Synthesis of 3,4,6-tri-O-acetyl-β-D-mannopyranose 1,2-orthoacetates (I) from 2,3,4,6-tetra-O-acetyl-α-D-mannopyranosyl bromide (II) and various alcohols in the presence of pyridine and substituted pyridines is described. 2,6-Lutidine is a particularly effective acid acceptor in these condensations, and the use of chloroform as a diluent is advantageous. The lutidine-buffered system has afforded a good yield of orthoacetate (I) with several alcohols that barely react with II in the presence of silver ion; this difference is attributed to the dominance of side reactions under the latter conditions. The N-bases also promote a more highly stereoselective orthoester synthesis than does the silver-catalyzed reaction, leading to formation of the OR-exo-diastereoisomer almost exclusively.
Phytochemical and FT-IR Spectral Analysis of Certain Bamboo Species of SouthIndia
Bamboo with its varied uses has historically been an integral part of livelihoods and lifestyles in India. The present study was carried out to characterize the bioactive constituents present in the leaf extracts of certain bamboo species using Fourier transform infrared spectroscopic analysis (FT-IR). The various solvent extracts of various bamboo leaves subjected to qualitative analysis showed the availability of phytoconstituents including alkaloids, phenolic compounds, flavonoids, saponins, glycosides, terpenoids, steroids, coumarins and phytosterols. Quinones were completely absent in all the five bamboo species. The FT-IR spectrum confirmed the presence of sulphides (SS), phenols (C-O), aromatic compounds, thiols (S-H), aliphatic compounds (C-Cl) and amines (NH) in different bamboo species. The present investigation has also opened avenues for further research into the development of potent phytomedicines from different bamboo species.