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Eudesmane Synthesis Essay

Abstract

The Mizoroki-Heck reaction was applied to substrates derived from isocostic and ilicic acids, important sesquiterpene components of Dittrichia viscosa L. Greuter that were extracted directly from plant material collected in Morocco. After optimization of the metallo-catalysis conditions, various aryl-groups were successfully introduced on the exocyclic double bond with an exclusive E-configuration and without racemization. View Full-Text

Keywords: eudesmane; isocostic and ilicic acids; Dittrichia viscosa L. Greuter; sesquiterpenes; Mizoroki-Heck reactioneudesmane; isocostic and ilicic acids; Dittrichia viscosa L. Greuter; sesquiterpenes; Mizoroki-Heck reaction

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MDPI and ACS Style

Zaki, M.; Akssira, M.; Berteina-Raboin, S. Modification of Natural Eudesmane Scaffolds via Mizoroki-Heck Reactions. Molecules2017, 22, 652.

AMA Style

Zaki M, Akssira M, Berteina-Raboin S. Modification of Natural Eudesmane Scaffolds via Mizoroki-Heck Reactions. Molecules. 2017; 22(4):652.

Chicago/Turabian Style

Zaki, Mohamed; Akssira, Mohamed; Berteina-Raboin, Sabine. 2017. "Modification of Natural Eudesmane Scaffolds via Mizoroki-Heck Reactions." Molecules 22, no. 4: 652.

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Structure Elucidation

Purification of the 95% EtOH extract from the fruits of D. carota L., using combinations of silica gel, ODS and Sephadex LH-20 column chromatography, gave one new sesquiterpene 1 (Figure 1), which structure was completely established by various spectroscopic analyses and MS studies.

Figure 1. Structure, key H-1H COSY (─) and HMBC correlations (H→C) of compound 1.

Figure 1. Structure, key H-1H COSY (─) and HMBC correlations (H→C) of compound 1.

Compound 1 (44.0 mg, yield: 0.022 %) was obtained as a colorless oil, [α]D22 +14.6° (MeOH; c 0.7). Its molecular formula was determined as C15H28O3 by HRESIMS (m/z 279.1930 [M+Na]+). The 13C-NMR data, in combination with analyses of the DEPT and HMQC spectra, revealed the presence of three tertiary methyls, six methylenes (one of which was oxygenated), four methines and two quaternary carbons (which were all oxygenated). Further, the 1H-NMR spectrum showed a set of signals including three tertiary methyl signals at δH 1.14 (3H, s, Me-11), 1.13 (3H, s, Me-13) and 1.10 (3H, s, Me-14), and one hydroxymethyl signals at δH 3.68 (1H, dd, J = 10.6, 6.2 Hz, H-15) and 3.42 (1H, dd, J = 10.6, 8.4 Hz, H-15). The three oxygenated carbon signals in the 13C-NMR spectrum (at δC 73.2, 75.2 and 63.9 ppm) were assigned to C-6, C-12 and C-15, respectively. The large C7–C8–C9–C10–C1(­–C15)–C2–C3–C4–C5 partial structure unit was deduced from the detailed analyses of 1H-1H COSY and HMQC spectral data of 1 (Figure 1). Interpretation of the HMBC spectral data led to the connectivities of the partial unit mentioned above and tertiary methyls coupled with quaternary carbons to construct the planar structure of compound 1. The HMBC correlations from δH 1.13 (Me-13) to δC 50.4 (C-8) and 75.2 (C-12), as well as from δH 1.10 (Me-14) to δC 50.4 (C-8) and 75.2 (C-12), indicated the existence and location of the isopropyl group at C-8. The attachment of the remaining methyl at C-6 was deduced on the basis of the HMBC correlations from δH 1.14 (Me-11) to δC 55.6 (C-5), 73.2 (C-6) and 46.6 (C-7). The stereochemistry of 1 was confirmed by careful assignment of NOESY data (Figure 2). The NOESY correlation between δH 1.70 (Hαax–5) and δH 2.36 (Hβ ax–10) was not observed, indicating that the A/B-ring linkage was a trans-configuration. The α-orientation of a hydroxymethyl group was suggested by the NOESY correlations for CH2α ax-15 (δH 3.68, 3.42)/Hα eq–2 (δH 1.36), Hβ eq–1 (δH 2.15)/Hβ ax–2 (δH 1.70) and Hβ ax–10 (δH 2.36). It was also supported by no NOESY correlation between CH2α ax-15 and Hβ ax–10. Furthermore, the NOESY correlation between Hβ ax–7 (δH 1.85) and Hβ eq–8 (δH 1.56) indicated the isopropyl group was α-orientated. In addition, the β-orientation of Me-11 and the α-configuration of OH–6 were determined by the NOESY correlation between Meβ ax-11 and Hβ eq–7. Based on the above results, the structure of 1 was established as (1α,5α,8α,10β)-decahydro-6α-hydroxy-8α,8α,6β-trimethyl-1,8-naphthalene-dimethanol, which is a new compound that we have named daucucarotol.

Figure 2. Key NOESY correlations (H→H) of compound 1.

Figure 2. Key NOESY correlations (H→H) of compound 1.

Table 1.1H- and 13C-NMR Data (500 and 125 MHz, resp.; CD3OD) of 1. δ in ppm, J in Hz.

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