Novel synthetic strategy toward abietane and podocarpane-type diterpenes from (−)-sclareol: synthesis of the antitumor (+)-7-deoxynimbidiol

Euphonoids A-G, cytotoxic diterpenoids from Euphorbia fischeriana

Seven previously undescribed polycyclic diterpenoids, euphonoids A-G, including four ent-abietanes, two ent-atisanes, and one ent-kaurene, along with 26 known analogues were isolated from the roots of Euphorbia fischeriana. The structures of the undescribed compounds were elucidated by spectroscopic analysis, ECD calculations, and single crystal X-ray diffraction. Besides, the structure of a previously reported ent-abietane diterpenoid, fischeriabietane A, was revised. All the isolates were screened for the cytotoxicities against five cancer cell lines. Euphonoid A, fischeriabietane A, 11-oxo-ebracteolatanolide B, caudicifolin, jolkinolide B, and methyl-8,11-3-dihydroxy-12-oxo-ent-abietadi-13,15(17)-ene-16-oate showed significant inhibitory activities against human prostate cancer C4-2B and C4-2B/ENZR cell lines, with IC₅₀ values being less than 10 μM. The brief structure-activity relationships (SARs) of these diterpenoids were also discussed.

Synthesis of Novel Podocarpa-8,11,13-Triene-7- and 13-Nitriles and Evaluation of their Anti-Inflammatory and Cytotoxic Activity

A series of novel podocarpa-8,11,13-triene-7- and 13-nitriles were prepared from the naturally occurring labdane diterpenoid (+)-manool, using podocarp-8(14)-en-13-one and 13-methoxypodocarpa-8,11,13-trien-7-one as key intermediates and TMSCN and acetonitrile as source of the nitrile. The synthesised compounds were screened for cytotoxicity against mouse macrophage cell line (RAW 264.7), human colon adenocarcinoma cell lines (HT-29) and human prostate adenocarcinoma cell lines (PC3) and for anti-inflammatory, as measured by the inhibition of nitric oxide (NO) production by RAW cells. 7-Oxopodocarpa-8,11,13-triene-13-nitrile exhibited significant inhibition of NO production (IC50 = 6 μM) and was not cytotoxic.

Synthesis and biological evaluation of ( - )-13,14-dihydroxy-8,11,13-podocarpatrien-7-one and derivatives from (+)-manool

13,14-Dihydroxy-8,11,13-podocarpatrien-7-one (1) and a series of ring C aromatic diterpene derivatives were synthesised from (+)-manool (4) and evaluated for their cytotoxic, leishmanicidal and trypanocidal activities. Our results indicated that compound 1 and other podocarpane-type intermediates are cytotoxic. Cleavage of C6-C7 bond of compound 7 improved cytotoxic activity, indicating that, in particular, the 6,7-seco-podocarpane-type compound 20 might serve as a lead compound for further development.

Facile Access to Optically Active Ring C Aromatic Diterpene Derivatives from (+)-Manool. First Synthesis of 13,14-Dihydroxy-8,11,13-podocarpatrien-7-one

14,15,17-Trinorlabdan-8,13-dione 6 was efficiently synthesized via ozonolysis of (+)-manool (4) followed by treatment with aqueous NaOH in the presence of tetra- n-butylammonium bromide as catalyst. This protocol has the advantages of high yield, mild conditions and simple procedure. Utilizing this strategy, the first enantiospecific synthesis of 13,14-dihydroxy-8,11,13-podocarpatrien-7-one (1), a constituent of Taiwania cryptomerioides and Celastrus paniculatus, was achieved starting from (+)-manool (4) after a four-step sequence in 24% overall yield.

Terpenoids from root bark of Celastrus orbiculatus

Phytochemical investigation of root bark of Celastrusorbiculatus afforded 10 terpenoids and eight known compounds. Their structures were established on the basis of spectroscopic and chemical methods. Celastrol and its dimers and adducts displayed moderate inhibitory activity against T cell proliferation. The reaction of celastrol under acidic conditions was undertaken, and a mechanism is presented, which may help towards modification of its structure and elucidation of the biogenetic routes to natural celastrol derivatives.

Facile Access to Optically Active Ring C Aromatic Diterpenes from (+)-manool. Synthesis of (+)-13-Hydroxypodocarpa-8,11,13-Triene, (+)-7-Deoxynimbidiol and (+)-Nimbidiol

A practical method for the synthesis of naturally occurring ring C aromatic diterpenes from (+)-manool via key intermediate β-enone is described. The natural (+)-13-hydroxypodocarpa-8,11,13-triene, the antitumour (+)-7-deoxynimbidiol, and (+)-nimbidiol were prepared in good overall yields.