Synthesis of Monoterpene Piperidines from the Iridoid Glucoside Antirrhinoside

Abstract

Synthesis of five novel piperidine monoterpene alkaloids (17−21) using the iridoid glucoside antirrhinoside (4) as a synthon is described. Two strategies for their preparation were investigated: the first possible pathway involved an intermediate diol, 13, from which the piperidine ring was expected to be constructed via reaction of its ditosylate with an amine; the second strategy involved a double reductive amination as the key step to the piperidine ring, which proved successful. The stereochemistry of C-5 and C-9 in the obtained piperidine monoterpenes was the same as that reported for α-skytanthine (3), a known isolate from Skytanthus acutus (Apocynaceae).

Efficient Conversion of Aucubin into 6-epi-Aucubin

“…Iridoids represent a large group of natural monoterpenoids, which can be advantageously used as starting material for the chiral pool synthesis of various bioactive compounds. − For instance, the synthesis of chiral prostanoids from iridoid glycosides is well documented. − Aucubin ( 1 ) is often used as starting material in these syntheses, because it can be readily extracted in large amounts from the fruits or leaves of Aucuba japonica Thunb . (Cornaceae).…”

NMR, LC-MS Characterization of Rydingia michauxii Extracts, Identification of Natural Products Acting as Modulators of LDLR and PCSK9

“…Diagnostic HMBC correlations were observed from H-4 with C-6, C-9 and from H-9 (δ 2.27) with C-4, C-8, C-1 and from the methyl group C-10 (δ 1.56) with C-8, C-7 and C-9 supporting the presence of cyclopentan-pyran iridoid nucleus. The coupling constant of H-1 (8.5 Hz) and the NMR assignments confirm the structure of antirrhinoside [ 33 ]. The quantification of compound 3 was perform by NMR.…”

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

“…On the other hand, we obtained a mixture of two isopropylidene derivatives (7 and 8) from compound 5 under the same protection conditions (Scheme 2), of which compound 8 has been reported previously. [ The structures of compounds 6, 7, and the already known 8 [30] were established on the basis of their 1 H and 13 C NMR spectra (see Exp. Section), from which it could readily be deduced where the acetonide had been formed.…”