Gaditanone, a Diterpenoid Based on an Unprecedented Carbon Skeleton Isolated from Euphorbia gaditana

Abstract

A novel diterpenoid, gaditanone (2), which possesses an unprecedented 5/6/4/6-fused gaditanane tetracyclic ring skeleton, and a new jatrophane (1) were isolated from the aerial parts of Euphorbia gaditana. The chemical structures and absolute configurations were determined by extensive spectroscopic NMR studies and ECD data analysis. A proposed biosynthetic pathway is presented for compound 2.

The value of universally available raw NMR data for transparency, reproducibility, and integrity in natural product research

“…In general, 13 C NMR spectra are less prone to the problems outlined above, but even there one sees occasional misinterpretation of an impurity signal and typos in transcribed tables of chemical shifts are plentiful. For example, a complex diterpenoid, gaditanone, ( 28 ) possessing an unprecedented 5/6/4/6-fused tetracyclic ring skeleton, was recently isolated and characterized by solution NMR,102 with its only carbonyl carbon, C-7, assigned the chemical shift value of 206.6 ppm. The DU8+ calculated value for this carbonyl carbon is 213.8 ppm, indicative of misassignment.…”

Unraveling Plant Natural Chemical Diversity for Drug Discovery Purposes

“…Among these strategies, it seems that the following ones could help solve some of the difficulties linked to NP discovery programs. The first one focuses on gaining ; AA: gaditanone (Flores-Giubi et al, 2017); AB: ingenane-type diterpenoid, euphorkan A ; AC: jatrophane-type ester ; AD: dideoxyphorbol ester ; AE: diterpenoid alkaloid sooneuphoramine (Gao and Aisa, 2017); AF: jatrophane-type diterpenoid (Rédei et al, 2018); AG: abietane-lactone-and nor-rosane-based heterodimeric terpenoids . Note that the stereospecificity of the compounds was not given, as many different compounds were described in each of those references.…”

Euphorbia Diterpenes: An Update of Isolation, Structure, Pharmacological Activities and Structure–Activity Relationship

“…The newly reported diterpenoids structures led to new information about their biological activities and their biogenesis in plants. Plants newly investigated within this time frame were E. kopetdaghi [ 25 ], E. sanctae-catharinae [ 26 ], E. gaditana [ 27 ], E. saudiarabica [ 28 ], and E. glomerulans [ 29 ].…”

“…Others were E. neriifolia [ 42 ], ( n = 32), E. lathyris ( n = 21) [ 31 ] ( n = 28), E. kansui [ 53 ] ( n = 23), E. stracheyi [ 32 ] ( n = 22), E. peplus [ 38 ] ( n = 22), E. antiquorum [ 34 ], ( n = 21) and E. marginata [ 41 ] ( n = 20). While other species reported only one or two diterpenes such as E. gaditana [ 27 ] ( n = 1), E. kopetdaghi [ 25 ] ( n = 2), E. aellenii [ 39 ] ( n = 2), E. pilosa ( n = 2) and E. grandicornis ( n = 2) ( Table 1 ). Anticancer, chemoreversal abilities, and anti-inflammatory activities were the most-studied biological studies.…”

“…Within the review period, over 200 different polycyclic diterpenes were described, including abietanes ( 1 – 5 ) [ 38 , 68 ], atisane ( 6 ) [ 35 ], cembranes ( 7 – 9 ) [ 33 , 44 ]; ent -abietanes ( 10 – 28 ) [ 34 , 38 , 47 , 59 ], ent -atisanes ( 29 – 41 ) [ 32 , 33 ], ent -labdanes ( 68 – 72 ) [ 38 , 51 ], ent -isopimaranes ( 42 – 64 ) [ 43 , 45 , 69 , 70 ], ent -kauranes ( 65 – 67 ) [ 33 ], ent -rosanes ( 73 – 87 ) [ 45 , 46 , 71 ], gaditanone ( 88 ) [ 27 ], and kaurane ( 247 ) [ 31 , 66 ]. Atisanes and cembranes were the least dominant subclasses, as only one new atisane, atisane-3-oxo-16 α ,17-diol ( 6 ) [ 35 ], from E. kansuensis and three cembranes diterpenes, euphopane C ( 7 ) from E. pekinensis [ 44 ], euphoroylean A ( 8 ), and B ( 9 ) from E. royleana [ 33 ], were isolated.…”