Reassignment of NMR spectra and conformational study of the sesquiterpene lactone goyazensolide

Abstract

We describe the reassignment of 13C NMR signals of goyazensolide based upon 1D and 2D techniques, and discuss its conformation and stereochemistry as obtained from the analysis of its proton spin–spin coupling constants, NOE measurements and molecular mechanics calculations using MM3* force field. Copyright © 2001 John Wiley & Sons, Ltd.

Cytotoxic and NF-κB inhibitory sesquiterpene lactones from Piptocoma rufescens

“…Purification of the first fraction gave a new compound, rufesolide C ( 5 ), and five known compounds, 15-deoxygoyazensolide ( 10 ), 4 2',3'-dihydro-15-deoxygoyazensolide ( 11 ), 5 lychnopholide ( 12 ), 6 4,5-dihydrolychnopholide ( 13 ), 7 and eremantholide C. 8 Separation of the second fraction produced three new compounds, rufescenolides A and B ( 1 and 2 ) and rufesolide D ( 6 ), and a known compound, 5-epiisogoyazensolide ( 9 ). 9 Work up of the third fraction afforded three known compounds, goyazensolide ( 8 ), 10 [3-(3,5-dimethoxy-4-hydroxyphenyl)]-1-propanol- trans -coumarate, 3 and 4'-methoxy-5,7,3'-trihydroxyflavone. 11 Finally, separation of the fourth fraction yielded a further quantity of goyazensolide ( 8 ), 10 in addition to 3-(4-hydroxyphenyl)-1-propanol- trans -coumarate, 12 4'-methoxy-3,5,7,3'-tetrahydroxyflavone, 11 3-methoxy-5,7-4'-trihydroxyflavone, 11 and 3,4'-dimethoxy-5,7-3'-trihydroxyflavone.…”

“…9 Work up of the third fraction afforded three known compounds, goyazensolide ( 8 ), 10 [3-(3,5-dimethoxy-4-hydroxyphenyl)]-1-propanol- trans -coumarate, 3 and 4'-methoxy-5,7,3'-trihydroxyflavone. 11 Finally, separation of the fourth fraction yielded a further quantity of goyazensolide ( 8 ), 10 in addition to 3-(4-hydroxyphenyl)-1-propanol- trans -coumarate, 12 4'-methoxy-3,5,7,3'-tetrahydroxyflavone, 11 3-methoxy-5,7-4'-trihydroxyflavone, 11 and 3,4'-dimethoxy-5,7-3'-trihydroxyflavone. 11 The structures of the cytotoxic sesquiterpene lactones isolated ( 1–13 ) are shown in Fig.…”

Complete ¹H and 13C NMR structural assignments for a group of four goyazensolide-type furanoheliangolides

“…In some cases, only the use of J-resolved experiments proved able to determine multiplicity. 2D experiments allowed the unequivocal assignments of 13 C NMR shifts. Despite the fact that a spectral assignment study has been published on goyazensolide (3), 13 the data in the cited paper failed to include experimental J values or 2D NMR data.…”

“…2D experiments allowed the unequivocal assignments of 13 C NMR shifts. Despite the fact that a spectral assignment study has been published on goyazensolide (3), 13 the data in the cited paper failed to include experimental J values or 2D NMR data. In addition, some J values were missing (such as J(3',4'a) and J (3',4'b)) and some differed from the experimental values (such as J(5,15a) and J (5,15b)).…”

“…Further to our research group interest on sesquiterpene lactones, 1,[8][9][10] we present this study of four furanoheliangolides: lychnofolide (1); centratherin (2); goyazensolide (3) and goyazensolide acetate (4) (Figure 1). All substances were thoroughly structurally studied by NMR experiments including 1 H NMR, 13 C NMR { 1 H}, COSY, HMQC and HMBC.…”