Cardenolides comprise an important family of natural steroids with a wide spectrum of biological activities. Although 19-hydroxysarmentogenin-3-O-α-L-rhamnoside (1a) and trewianin (1b) were structurally determined to have cardenolide structures, their biological activities have not been evaluated. The 6/6/ 6/5-membered ABCD-ring systems of both 1a and 1b are decorated by a β-oriented C17-butenolide, three C11,14,19-hydroxy groups, and a C3−O-L-rhamnoside moiety. On the other hand, 1a and 1b are epimeric at the C5-position. The structures of 1a and 1b were assembled from four simple fragments by applying a convergent and unified strategy. The AB-ring 10a/b and the D-ring 8/9 were tentatively tethered at the acetal moiety, and a subsequent stereoselective 6-exo radical reaction linked the two fragments. Next, an aldol reaction enabled simultaneous introduction of three new stereocenters of the C-rings of 5aa and 54. Attachment of the C17-butenolide led to aglycons 2a and 2b. L-Rhamnose was then installed into 2a and 2b to yield the targets 1a and 1b, respectively. Finally, the growth inhibitory activity of 1a, 1b, 2a, and 2b was assessed against MCF-7 human breast carcinoma cells. The significantly higher activities of 1a and 1b in comparison to 2a and 2b demonstrated the biological importance of the monosaccharide substructure.
A convergent total synthesis of ouabagenin, an aglycon of cardenolide glycoside ouabain, was achieved by assembly of the AB-ring, D-ring and butenolide moieties.
In the present work, TDSC of 1Htri, 1Htri-CH3 and 1Htri-NH2 were determined by using SC-DSC and Molecular orbital calculations (MO) was used to clarify thermal decomposition mechanism and stability criteria of pathway of 1Htri, 1Htri-CH3 and 1Htri-NH2 were d.TDSC of 1Htri, 1Htri-CH3 and 1Htri-NH2 were determined from the lower ΔEa of thermal decomposition pathway model as proton transfer combine with cleavage bond. The determined TDSC were 297 ºC of 1Htri, 114 ºC of 1Hti-CH3 and 289 ºC of 1Htri-NH2.There results were corresponded with the measured TDSC as were 338 ºC of 1Htri, 172 ºC of 1Hti-CH3 and 293 ºC of 1Htri-NH2, respectively.The results reveal that our approach thermal decomposition pathway model as combination of proton transfer and cleavage bonds of 1Htri, 1Htri-CH3 and 1Htri-NH2 cab be possible to expand and control the application of these compounds.
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