Carbon‐13 NMR spectra of kauranoid diterpenes

Abstract

Carbon-13 NMR spectra of a number of (-)-ent-kauranoids have been studied. An unambiguous selfconsistent assignment of resonances has been made by considering the changes in chemical shifts produced by the change of substituent(s).A new kauranoid diterpene, didymooblongin (1) was isolated' along with (-)-enf-16-kauren-19-oic acid' (2) and (-)-ent-16a-kaurano13 (3) from the whole plant Didymocarpus oblonga. Didymooblongin [(-)-ent-7P-hydroxy-16-kauren-19-oic acid] has been shown4 to be an intermediate in the metabolic transformation of (-)-ent-kaur-16-ene to gibberellic acids in the mould Gibberella fujikuroi. We report here the I3C NMR spectral assignments of 1 and 2 as well as those of some closely related compounds (4-12). Carbon-13 N M R data of (-)-ent-16-kauranyl acetate (13) are also presented. The assignments were made by comparing the effects of the change of one functional group to another. Once the spectral assignments of (-)-ent-16-kauren-19-oic acid (2) were made it was very simple9 R' = COOH, R2 = a-H, 6-OAc, R3 = CH, 10 R' = COOH, R2 = 0, R3 = CH, 12 R' = CH,OAc, RZ = a-H, (3-OAc, R' = CH, 13 R' = CH,, R2 = H,, R3 = a-OAc, @-CH, 14 R' = CH,, R2 = H,, R3 = CH, 15 R' = CH,, R2 = H,, R' = 0 16 R' = COOH, RZ = H,, R3 = 0 11 R'=CH,OH, R 2 = a -H , @-OH, R'=CH,

A New Abietane and Two Dimeric Abietane Diterpenes from the Black Heartwood of <i>Cryptomeria japonica</i>

“…cubenol (9), 15) epi-cubenol (10), 16,17) cubebol (11), 16,17) epicubebol (12), 18) gleenol (13), 19) b-elemol (14), 20) cryptomerione (15), 21) 7 (14),10-bisaboladien-1-ol-4-one (16), 22) 2,7(14),10-bisabolatrien-1-ol-4-one (17), 23) 7 (14),10-bisaboladien-1,4-diol (18), 24) cryptomeridiol (19), 25) sandracopimaradiene (20), 26) sandaracopimarinal (21), 27) sandaracopimarinol (22), 28) sandaracopimaric acid (23), 29) 8 [14],15-pimaradiene-3-ol (24), 30) 18-nor-8 [14],15-isopimaradien-4-ol (25), 31) sandaracopimarinol acetate (26), 31) 16-phyllocladanol (27), 32) 7,13-abietadiene (28), 33) abietatriene (29), 34) ferruginol (30), 35) 6,7-dehydroferruginol (31), 36) sugiol (32), 37) hinokiol (33), 37) 19-hydroxyferruginol …”

Carbon‐13 NMR lanthanide induced shifts and T1 studies of the conformation of friedelin

“…The assignments of the I3C signals were taken from Ref. 6. We used Pr(fod), as the shift reagent because it has been s h o~n~,~ to produce a smaller contact contribution to the shift compared with the more commonly used Eu(fod), .…”

“…6. The methylene and methine carbons showed the maximum NOE, and the NT, values for these carbons were nearly the same (1.4 s), indicating nearly isotropic motion for the molecule.…”

Efecto citotóxico de algunos compuestos naturales aislados de plantas Laureaceae y derivados sintéticos

“…Test compounds from natural sources, 1-14, and synthetic benzofurans, 15-17, were obtained in previous studies (19)(20)(21)(22)(23)(24)(25). Here the O-methylation of liliflol A, 1, affording 18, and the racemic resolution of synthetic (±)-cinerin A into 19 and 20 are decribed.…”

“…Detailed extraction and isolation processes, and spectroscopic features for the test compounds were previously reported (19)(20)(21)(22)(23)(24) 8 (19), ocophyllol C 9 (19), kadsurenin C 10 (22), nectamazin C 11 (23), meso-and threo-3,4,5,3',4',5'-hexamethoxy-8.8'-neolignan 12-13 and kaurenoic acid 14 (24). Compounds 2, 5-7 were isolated from P. cinereum, compounds 4, 8-9 from O. macrophylla, and compounds 1, 3, 10-11 from N. amazonum, using conventional chromatographic methods.…”