DDQ-promoted dehydrogenation from natural rigid polycyclic acids or flexible alkyl acids to generate lactones by a radical ion mechanism

Abstract

A novel and facile DDQ-mediated dehydrogenation from natural rigid polycyclic acids or flexible alkyl acids to generate lactones is described. The formation of lactones proceeds by a radical ion mechanism, which has been established by DPPH˙-mediated chemical identification, ESR spectroscopy and an enol intermediate trapping.

Synthesis of CDDO–Amino Acid–Nitric Oxide Donor Trihybrids as Potential Antitumor Agents against Both Drug-Sensitive and Drug-Resistant Colon Cancer

“…1), and others. [26][27][28][29] These SOADs have strong anti-tumor activity by inhibiting tumor cell proliferation and inducing cancer cell apoptosis. 30 Recent studies show that OA and its derivative methyl 3,11-dioxoolean-12-en-28-olate (DIOXOL, Fig.…”

Cytotoxicity, Hemolytic Toxicity, and Mechanism of Action of Pulsatilla Saponin D and Its Synthetic Derivatives

“…Finally, hydrolysis of 8 gave 9 , which has C-12 oxo and C-28 COOH groups rather than a 28,13-lactone. Oxidation of 8 with DDQ (2,3-dichloro-5,6-dicyano-1,4-benzoquinone) in anhydrous benzene, 20 followed by hydrolysis, provided 10 with a C-12 oxo group and 28,13-lactone. The synthetic methods used to obtain compounds 12−18 are illustrated in Scheme 2.…”

An efficient synthesis of methyl 2-cyano-3,12-dioxoursol-1,9-dien-28-oate (CDDU-methyl ester): analogues, biological activities, and comparison with oleanolic acid derivatives

“…Finally, direct treatment of 35 with DDQ in refluxing benzene provided lactone 38 in 71% yield (Scheme 6). 26…”

“…1 H NMR (500 MHz, CDCl 3 ) δ 5.80 (s, 1H), 3.56 (s, 3H), 3.13 (dd, 1H, J 1 = 11.6 Hz, J 2 = 4.5 Hz), 2.83 (dd, 1H, J 1 = 11.4 Hz, J 2 = 3.0 Hz), 2.32 (d, 1H, J = 3.8 Hz), 2.25 (brs, 1H), 1.78-1.91 (m, 2H), 1.37-1.72 (m, 12H), 1.24-1.35 (m, 2H), 1.03-1.20 (m, 2H), 1.09 (s, 3H), 1.04 (s, 3H), 1.01 (s, 3H), 0.95 (s, 3H), 0.79 (d, 3H, J = 6.1 Hz), 0.73 (s, 3H), 0.65 (d, 3H, J = 6.6 Hz); 13 C NMR (500 MHz, CDCl 3 ) δ 201.0, 179.9, 178.4, 123.0, 77.9, 52.0, 51. Methyl 3,12-dioxoursol-9(11)-en-28-oate (26). To a stirred solution of alcohol 25 (4.9 g, 10.1 mmol, 1.0 equiv.)…”