Conversion of asperuloside to optically active prostaglandin intermediates

Abstract

The iridoid glycoside asperuloside has been converted by both oxidative and reductive routes to optically active prostanoid intermediates. The enol ether group was oxidized to a lactone by I2/PDC followed by in situ reduction of the iodo lactone with thiosulfate. Hydrolysis and decarboxylation then gave the 11-homologue of the Corey lactone aldehyde. Wadsworth-Emmons reaction of this added the lower side chain as expected. Alternatively, tetrahydroasperuloside was converted to a tetracyclic acetal by acid treatment. This was selectively cleaved by acetyl chloride/TiCl4 to a hemiacetal which underwent Wadsworth-Emmons reaction, followed by oxidation and decarboxylation to give the same intermediate prepared by the lactone route.

Stereoselective Conversion of Aucubin into Polyfunctionalized Tetrahydro‐1H‐cyclopenta[c]furan Glucosides

“…Under those conditions, a 7 : 3 mixture of iodolactones 17 (4R) and 18 (4S) was obtained from 12, whereas both 9 and 10 gave the corresponding (4R)-iodolactones 19 and 20, respectively, as single reaction products. In both 19 and 20, the configuration at C(4) was deduced from the NOE between HÀC(1) and HÀC (4). Coupling constants clearly indicate that the conformation adopted by the cyclopenta[c]pyran system of 6-epi compounds 19 and 20 strongly differ from that of 17 [12].…”

Chiral Synthons from the Iridoid Glucoside Antirrhinoside − Synthesis of a Carbocyclic Homonucleoside Analogue

“…[11Ϫ14] In particular, aucubin, [15Ϫ24] asperuloside, [25] and catalpol [26Ϫ29] have been used in the synthesis of prostaglandin analogues, while aucubin constituted the chiral starting material in the synthesis of two carbocyclic nucleosides. [11Ϫ14] All of these are iridoids that are present in large quantities in plants and they are easily extracted and purified.…”

An Iridoid Glucoside and the Related Aglycones from Cornus florida

“…This coupling constant is consistent with that observed for the cis -fused tricyclic iridoids semperoside ( J = 10.5 Hz), 9-hydroxysemperoside ( J = 11.4 Hz), and dihydrobrasoside ( J = 10.5 Hz), 24 together with the dilactone compounds, asperuloside tetraacetate lactone ( J = 9.8 Hz) and dihydroasperuloside tetraacetate lactone ( J = 10.0 Hz), produced from the oxidation of the iridoid glucoside asperuloside. 26 Thus, the configuration of cornolactone B ( 3 ) was defined as 4 S ,5 S ,6 S ,8 S ,9 R .…”