Quinolizidine/indolizidine alkaloids from the seed of Camoensia brevicalyx

Waterman, Peter G.; Faulkner, D.

doi:10.1016/0031-9422(82)80046-0

Cited by 15 publications

(7 citation statements)

References 6 publications

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“…[10]. For a detailed comparison of our NMR data with literature NMR data of isolated 10 , [4e,6g] see Supporting Information.…”

Section: Methodsmentioning

confidence: 97%

“…[4a]: [α] D 27 =−73 ( c =1.13, EtOH)}; 1 H NMR (CDCl 3 , 500 MHz): δ=4.57 (d, J =13.1 Hz, 1 H, 10‐ H H), 3.34 (t, J =7.0 Hz, 1 H, 6‐H), 2.73 (m, 2 H, 14‐ H H, 16‐ H H), 2.63 (d, J =13.1 Hz, 1 H, 10‐H H ), 2.43–2.20 (m, 5 H, 3‐H 2 , 11‐H, 14‐H H , 16‐H H ), 2.02 (m, 1 H, 5‐ H H), 1.94 (s, 1 H, 9‐H), 1.85–1.68 (m, 6 H, 4‐ H H, 7‐H, 8‐ H H, 12‐H 2 , 13‐ H H), 1.63–1.45 (m, 3 H, 4‐H H , 8‐H H , 13‐H H ), 1.35 (d, J =12.5 Hz, 1 H, 5‐H H ); 13 C NMR (CDCl 3 , 125 MHz): δ=171.4 (C‐2), 64.6 (C‐11), 60.1 (C‐6), 54.5 (C‐14), 49.4 (C‐16), 47.6 (C‐10), 33.2 (C‐3), 33.2 (C‐7), 31.2 (C‐9), 28.9 (C‐8), 27.6 (C‐12), 27.6 (C‐5), 21.1 (C‐4), 20.1 (C‐13) ppm; IR (ATR):

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=2945, 2866, 1619, 1442, 1253, 1163, 1018, 916, 726, 641 cm −1 ; HRMS (ESI): m / z calcd for C 14 H 22 N 2 O+H + : 235.18049 [M+H] + ; found: 235.18016. For a detailed comparison of our NMR data with literature NMR data of isolated 11 , [4a,e] see Supporting Information.…”

Section: Methodsmentioning

confidence: 97%

“…In addition to the 'standard' (bis)quinolizidine alkaloids, a small number of atypical quinolizidine-indolizidine derivatives (7)(8)(9)(10)(11)(12) exists that possess an exo-or endo-fused pyrrolidine. [4] It is hypothesized that the smaller ring size results from a replacement of one molecule of l-lysine by l-ornithine (C 4 N source) during their biosynthesis. [5] The first member of this subclass, leontidine (7), was already isolated in 1932 from Leontice ewersmannii, [6] camoensine (10) [7] and camoensidine (11), [8] both first extracted from Camoensia maxima, followed in 1975.…”

Section: Introductionmentioning

confidence: 99%

“…NaOH (6 M, 3.5 mL) was added and the aqueous layer was extracted with CH 2 Cl 2 (20 × 9 mL). The combined organic layers were dried over Na 2 SO4 and concentrated under reduced pressure. The residue was purified by column chromatography (SiO 2 , CH 2 Cl 2 /MeOH/NH 3 (aq., 25 %) 100 : 0:0!90 : 9 : 1), providing the alcohol 27 as a colorless resin; yield: 61.1 mg (246 μmol, 81 %); R f = 0.14 (CH 2 Cl 2 /MeOH/NH 3 (aq., 25 %) 95 : 4.5 : 0.5); [α] D 25 = À 74.0 (c = 1.0, MeOH); 1 H NMR (CDCl 3 , 500 MHz): δ = 7.29 (dd, J = 9.0 Hz, 6.9 Hz, 1 H, 4-H), 6.44 (dd, J = 9.0 Hz, 1.0 Hz, 1 H, 3-H), 5.99 (dd, J = 6.8 Hz, 0.7 Hz, 1 H, 5-H), 4.14 (d, J = 15.8 Hz, 1 H, 10-HH), 3.89 (dd, J = 15.8 Hz, 6.5 Hz, 1 H, 10-HH), 3.68 (ddd, J = 11.0 Hz, 5.5 Hz, 4.2 Hz, 1 H, CHHOH), 3.54 (ddd, J = 11.0 Hz, 8.0 Hz, 3.0 Hz, 1 H, CHHOH), 3.32 (br.…”

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confidence: 99%

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Diastereodivergent Synthesis of the Quinolizidine‐Indolizidine Alkaloids of the Leontidine/Camoensine Family

et al. 2021

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Leontidine and camoensine, the main representatives of the small quinolizidine‐indolizidine alkaloid subgroup, are characterized by an inner bispidine system to which a 2‐pyridone and a pyrrolidine are fused on opposite sides. We efficiently synthesized both natural products from the commercially available and abundant alkaloid cytisine, which was converted into the key intermediate, N‐Boc‐11‐oxocytisine, by iodine oxidation and protection. Grignard addition, Paal‐Knorr type cyclization, and hydrogenation delivered endo‐pyrrolidine fused leontidine, while the reversed reaction order, viz. reduction, Sakurai allylation, and ring closure, afforded exo‐pyrrolidine annulated camoensine. Hydrogenation and deoxygenation of the pyridone moieties provided four further alkaloids, tetrahydroleontidine, camoensidine, 11‐epileontidane and leontidane. In addition, the artificial alkaloid isoleontidine, carrying an endo‐fused pyrrolidine on the same side as the pyridone, was prepared from C‐13 oxidized cytisine.

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“…[10]. For a detailed comparison of our NMR data with literature NMR data of isolated 10 , [4e,6g] see Supporting Information.…”

Section: Methodsmentioning

confidence: 97%

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Section: Methodsmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Diastereodivergent Synthesis of the Quinolizidine‐Indolizidine Alkaloids of the Leontidine/Camoensine Family

et al. 2021

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“…The upfield chemical shift observed for C-8 at 26.08 is characteristic for lupine alkaloids, reflecting the shielding effect due to its spatial proximity to N-12. This is typically encountered in quinolizidines in which H-9 and H-ll are trans-oriented to each other (12,13). In contrast in H-9/H-11 cisquinolizidines, C-8 is known to resonate at values greater than 30 ppm (12,13).…”

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confidence: 99%