Facile synthesis of tetrasaccharide fragments of bioactive Asterosaponins novaeguinosides I and II from starfish Culcita novaeguineae

Abstract

Simple and straightforward synthesis of tetrasaccharide fragments of novaeguinosides I and II, isolated from the starfish Culcita novaeguineae that showed significant in vitro cytotoxicity activity against two human tumor cell lines (leukemia K-562 and hepatoma BEL-7402) is reported. The tetrasaccharide moieties have been synthesized as their p-methoxyphenyl (PMP) glycosides by sequential glycosylation strategy using suitably functionalized thioglycoside donors employing sulfuric acid immobilized on silica (H2SO4-silica) as a Brönsted acid catalyst to work as a promoter for all glycosylation reactions. All intermediate steps are high yielding and the glycosylation steps are stereoselective.

An Expeditious Approach to the Synthesis of Novel Quinolino and Diazacino Condensed Analogues of Azepino [3, 2-b] Carbazole-2-one of Medicinal Interest

“…16 It is evident from the literature that heterocyclics that contain quinolones, 17 carbazoles, 18 azepinones 19 etc. in their molecules exhibit a wide variety of biological activities such as, anti-mycobacterial, 20 anti-leishmanicidal, 21 antitumor, 22 anti-proliferative 23 and anti-leukemic 24 etc. With a view to explore their pharmaceutical potential further, it occurred to as mind to undertake the synthesis of some such molecules which incorporated (a) quinoline-4-carboxylic acid and azepinone framework (b) diazocene pharmacophores on to the carbazole nucleus.…”

α/β-Stereo- and diastereoselective glycosylation with n-pentenyl glycoside donors, promoted by N-iodosuccinimide and catalyzed by chiral Brønsted acid

“…[3][4][5][6][7][8][9][10] Sulfuric acid immobilized on silica as BA in combination with N-iodosuccinimide (NIS) was utilized to activate a thioglycoside for the synthesis of tetrasaccharide fragments. [11][12][13] Furthermore, attempts at achieving α/β-stereoselectivity in glycosylation were made with chiral BAs (CBAs)activation. This involved the use of a tetrazole-amino acid ionic liquid, 9 chiral binaphthol (BINOL) phosphoric acids, [14][15][16] and peptides bearing carboxylic acid groups in combination with an MgBr 2 Lewis acid.…”