Fe(III) mediated oxidative radical cyclisation of cyclopropanone acetals

Improved synthetic route to enantiomerically pure samples of the tetrahydropyran-2-ylacetic acid core associated with the phytotoxic polyketide herboxidiene

“…12,20 (21.0 g, 98%) as a light-yellow oil. n max 3078, 2980, 2933, 1721, 1655, 1446, 1367, 1315, 1266, 1206, 1176, 1044, 989, 914, 852 cm -1 .…”

Total Syntheses of Rhodomolleins XX and XXII: A Reductive Epoxide‐Opening/Beckwith–Dowd Approach

“…To further extend the generality of this reductive epoxide‐opening/Beckwith–Dowd rearrangement process, the regioselective fragmentation of cyclopropanol 33 , which could be prepared from 12 in 75 % yield following Fernández‐Mateos’ procedure, was also conducted (Scheme ) . On the basis of seminal works by DePuy, Saegusa, and Narasaka, it was found that the cleavage of the C13–C16 bond could be significantly inhibited in the presence of Fe(NO 3 ) 3 and 1,4‐cyclohexadiene in DMF, affording a 5.4:1 mixture of 9 and 24 in 83 % yield (conditions a). More importantly, triol 9′ , a viable advanced intermediate en route to C12‐oxygenated grayanane diterpenoids of biological importance (such as grayanotoxin XI and rhodomollein XXVIII), was obtained as well in an even higher yield upon treatment of 33 with catalytic VO(acac) 3 under oxygen atmosphere (conditions b) .…”

Total Syntheses of Rhodomolleins XX and XXII: A Reductive Epoxide‐Opening/Beckwith–Dowd Approach

“…Further deprotection in the presence of PPTS furnished rhodomollein XX (5)in64% yield over three steps.S ynthetic 5 and 6 exhibited 1 Ha nd 13 CNMR spectra identical in all respects to those reported for the natural products. [29] On the basis of seminal works by DePuy,Saegusa, and Narasaka, [30] it was found that the cleavage of the C13-C16 bond could be significantly inhibited in the presence of Fe(NO 3 ) 3 and 1,4cyclohexadiene in DMF, [31] affording a5.4:1 mixture of 9 and 24 in 83 %y ield (conditions a). [29] On the basis of seminal works by DePuy,Saegusa, and Narasaka, [30] it was found that the cleavage of the C13-C16 bond could be significantly inhibited in the presence of Fe(NO 3 ) 3 and 1,4cyclohexadiene in DMF, [31] affording a5.4:1 mixture of 9 and 24 in 83 %y ield (conditions a).…”

“…[8] To further extend the generality of this reductive epoxideopening/Beckwith-Dowd rearrangement process,t he regioselective fragmentation of cyclopropanol 33,w hich could be prepared from 12 in 75 %yield following Fernµndez-Mateos procedure, [28] was also conducted (Scheme 4). [29] On the basis of seminal works by DePuy,Saegusa, and Narasaka, [30] it was found that the cleavage of the C13-C16 bond could be significantly inhibited in the presence of Fe(NO 3 ) 3 and 1,4cyclohexadiene in DMF, [31] affording a5.4:1 mixture of 9 and 24 in 83 %y ield (conditions a). More importantly,t riol 9' ', av iable advanced intermediate en route to C12-oxygenated grayanane diterpenoids of biological importance (such as grayanotoxin XI and rhodomollein XXVIII), [32] was obtained as well in an even higher yield upon treatment of 33 with catalytic VO(acac) 3 under oxygen atmosphere (conditions b).…”