New Quinoline Alkaloid Acusine and Crystal Structures of N -Methyl-2-Phenylquinolin-4-One and Pedicine from Haplophyllum
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NEW QUINOLINE ALKALOID ACUSINE AND CRYSTAL STRUCTURES OF N-METHYL-2-PHENYLQUINOLIN-4-ONE AND PEDICINE FROM Haplophyllum acutifolium
M. A. Eshonov,* Kh. A. Rasulova, K. K. Turgunov, and B. Tashkhodzhaev
The new natural 2-quinoline alkaloid acusine in addition to N-methyl-2-phenylquinolin-4-one and pedicine were isolated from Haplophyllum acutifolium. The structure of acusine was determined using IR and NMR spectral data. The structures of N-methyl-2-phenylquinolin-4-one and pedicine were proven by XSAs. Keywords: Haplophyllum acutifolium, Rutaceae, quinoline alkaloids, NMR spectroscopy, XSA. The alkaloids skimmianine and acutine and the lignane eudesmine were previously isolated from the aerial part of Haplophyllum acutifolium (DC.) G. Don. (Rutaceae) collected in the mountains of Turkmenia [1]. The aerial part of this plant collected during the vegetation period in June in Jizzakh Region, Republic of Uzbekistan, was studied by us. Previously, total alkaloids from H. acutifolium were separated by us to isolate the quinoline alkaloids skimmianine, evoxine, glycoperine, perfamine, haplamine, and the new base acutinine [2]. In continuation of studies on alkaloids from the aerial part of H. acutifolium, we isolated the alkaloids N-methyl-2phenylquinolin-4-one (1), pedicine (2), and a new base 3, which we called acusine. Known alkaloids 1 and 2 were identified by direct comparison with authentic samples (TLC, mixed mp) [3, 4]. Acusine (3) was a white crystalline base, mp 151°C. The IR spectrum of 3 showed absorption bands for O–COCH3 (1748 cm–1) and an aromatic ring (1594 cm–1). The PMR spectrum of 3 contained four resonances for aromatic protons, a 1H singlet at δ 5.98 ppm characteristic of quinolin-2-one H-3, a 1H multiplet at δ 7.83 ppm for H-5, and 1H multiplets at δ 7.14 and 7.13 ppm for H-6 and H-7, respectively. The spectrum also had resonances at δ 3.87 ppm for OCH3, 3.70 for NCH3, and 2.32 for H3C–C=O. OCH3 4
4a 1 8a
H3C C O
2
N O CH3
O 3
The chemical shifts (CSs) of resonances for C atoms were assigned based on DEPT spectra of acusine and a comparison with the published CSs of quinoline alkaloids [5], in particular pedicine (2) [4], which enabled the structure of the base to be proposed as 3, which was confirmed by the 13C NMR spectrum. The total 13C NMR and DEPT spectra showed resonances for 13 C atoms as six quaternary, four methine, and three methyl C atoms (Table 1). The quaternary quinoline ring atoms C-2, C-4, C-8, and C-8a and C-4a appeared in the 13C NMR spectrum at 164.66, 162.45, 137.62, 133.58, and 119.50 ppm, respectively. Acusine had structure 3 according to the spectral data. Previously, this base was synthesized from foliosidine [6]. S. Yu. Yunusov Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, e-mail: [email protected]. Translated from Khimiya Prirodnykh Soedinenii, No. 6, November–December, 2020, pp. 946–948. Original article submitted February 17, 2020. 1102
0009-3130/20/5606-1102
©2020
Springer Science+Business Media,
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