Ein zweiter Schwefel‐haltiger Stoff aus dem Milchsaft von Calotropis procera

Abstract

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Towards the synthesis of calotropin and related cardenolides from 3-epiandrosterone: A-ring related modifications

“…Scheme 2 Overview of the two concepts for the installation of the trans-diol moiety at C-2/C-3 and the aldehyde at C-19 starting from 3-epiandrosterone (12). While the first generation approach (red) is based on an epoxidation of the acetyl enol ether 16, the second generation approach (green) relies on a diastereoselective Sharpless dihydroxyation of 15 followed by a regioselective acetylation of C-3's hydroxyl group.…”

“…The presented work enables the regioselective C-H oxidation of the methyl group at C-19 followed by the subsequent introduction of the 2α,3β-trans-diol moiety in order to enable the connection to the sugar moiety. We faced two synthetic routes for the preparation of the precursor 14 for the remote C-H oxidation starting from commercially available 3-epiandrosterone (12). The first generation route based on traditional steroid chemistry could be replaced by a more convenient and efficient sequence of an asymmetric Sharpless dihydroxylation and a regioselective acetylation.…”

“…7 While digitoxin (1), digoxin (2) and ouabain (3) are attached via their 3β-OH group to the sugar moiety, the cardenolides calotropin (4) and their related cardenolides (5)(6)(7)(8)(9)(10) are connected by the 2α-and 3β-position to the sugar unit forming a 1,4-dioxane ring. [8][9][10][11][12][13][14][15] This double linkage of the steroidal pattern to the carbohydrate explains the unusual stability towards acids 16 and reduction. 17 Calotropin (4) and related cardenolides (5-10) bear moreover an aldehyde functionality at C-19 16,[18][19][20] that distinguishes For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/d0qo00269k a them from gomphoside derivatives and occurs occasionally in some cardenolide classes, for instance also in k-strophanthin.…”

“…As steroidal precursor, we chose commercially available 3-epiandrosterone (12) possessing already six of the eight required stereogenic centers. Nevertheless a couple of modifications at the A-ring of the steroid are required including the installation of the 2,3-trans-diol and the oxidation of C-19.…”

Calotropis procera accumulates Uzarigenin and Calotropagenin in response to environmental lighting and drought

“…These biological activities can be linked to a wide variety of classes of chemicals, the majority of which are found in the form of cardiac glycosides ( Khan and Malik, 1989 , Seiber et al, 1982 , Shaker et al, 2010 ), terpenes ( Bhutani et al, 1992 ), flavonoids ( Nenaah, 2013 ) and tannin ( Mossa et al, 1991 ). Calotropis procera has been used to isolate a variety of cardiac glycosides, including Calactin, Ascelpin, Uscharin, Calotoxin, Uscharidin, Frugoside, Voruscharin, Calotropin, and Uzarigenin ( Elgamal et al, 1999 , Hassall and Reyle, 1959 , Hesse and Lettenbauer, 1957 , Hesse and Ludwing, 1960 , Karale and Karale, 2017 , Pandey et al, 2016 , Shaker et al, 2010 ). These cardiac glycosides (CG) have been employed for decades in treating congestive heart failure disorders ( Jorgensen et al, 2003 , Smith, 1989 ).…”