Complete ¹³C NMR assignments for ent‐kaurane diterpenoids from Sideritis species

Abstract

In this work, the detailed NMR studies and full (13)C NMR assignments for five diterpenoids isolated from Sideritis caesarea and Sideritis athoa are described. The assignments are based on a combination of 1D and 2D NMR techniques including (1)H, (13)C, (1)H-(1)H COSY, gHSQC [(1)J(C,H)] and gHMBCδ(C) [(n)J(C,H)(n=2 and 3)] and NOESY experiments.

Flavonoid constituents of Sideritis caesarea

“…12,13 In a former study we reported 5 diterpenoids, all with the ent-kaurane skeleton, from the acetone extract of Sideritis caesarea. 11 The present study is the first report on the isolation and structure elucidation of its * Correspondence: halfonbe@boun.edu.tr flavonoid constituents. Although the flavone apigenin (2) and glycosylated flavonoids (3)(4)(5)(6)(7)(8) have been isolated from other Sideritis species, the trimethoxylated flavone penduletin (5,4'-dihydroxy-3,6,7-trimethoxyflavone)…”

Ent-kaurene Diterpenoids from Sideritis lycia with Antiviral and Cytotoxic Activities

“…Most of the chemical studies on Turkish Sideritis species, particularly for diterpenic structures have been carried out by Topcu's group including Sideritis athoa [22], S. argyrea [23], S. dichotoma [24], S. sipylea [24], S. trojana [25], S. leptoclada [26], S. stricta [27], S. tmolea [28], S. condensata [29], S. arguta [30], S. congesta [31], S. niveotomentosa [32], S. brevibracteata [33], and several other Sideritis species [34]. Antioxidant and anticholinesterase activities of ent-kaurane diterpenoids from Sideritis arguta and S. congesta were studied by Topcu group, and 7-epi-candicandiol and sideroxol showed the highest butyrylcholinesterase inhibitory activity among the screened compounds, including the standard compound galanthamine [30,31,33,35].…”

Cytotoxic and Anti-Inflammatory Effects of Ent-Kaurane Derivatives Isolated from the Alpine Plant Sideritis hyssopifolia

“…The relative configuration of 3 was confirmed by saponification (K 2 CO 3 /MeOH). The 1 H NMR spectrum of the resulting diol compound was compared with the published spectrum of ent-3β-7α-dihydroxykaur-16-ene [15], and a perfect match was obtained, thus confirming the relative configuration of compound 3. According to the sign of the CE on ECD spectrum, the same absolute configuration was attributed to compound 3.…”

“…After extraction by ethylacetate, drying over anhydrous sodium sulfate, concentration under vacuum, and HPLC purification (heptane/ethylacetate, 1:1, v/v), the known compound ent-3β-7α-dihydroxykaur-16-ene (0.46 mg, 100%) was obtained. The spectral data of synthetic ent-3β-7α-dihydroxykaur-16-ene were identical to those of the natural compound [15].…”

“…Except for siderol [9], diterpenoids have yet to be reported in S. hyssopifolia [10]. Because these compounds are commonly found throughout the Sideritis genus, we re-investigated the phytochemical composition of S. hyssopifolia and, as a result, isolated 12 compounds, eight of which are reported in this species for the first time, namely, siderol [9], sideridiol [9], siderone [11], ent-kaurene I [12], sideritriol [13], ent-15β,16β-epoxykauran-18-ol [14], epi-candicandiol [12], and ent-3β-7α-dihydroxykaur-16-ene [15]. Additionally, four new ent-kauranes were fully characterized ( Figure 1) using 1D and 2D NMR, MS, and ECD.…”