Short Total Synthesis of (±)-Galbulin and (±)-Isogalbulin Using Zirconium Chemistry

Zirconocene-Induced Cocyclisation/Elimination Reactions of 2-Heterosubstituted 1,6-Dienes and 1,6-Enynes

“…The lack of stereocontrol is in accord to that recently observed in cyclisation of a similar diene lacking the ethoxy group. 22 Five membered ring formation when fused to an aromatic ring (Table 2, entry 7) was poor yielding, but provided 19f as a single diastereoisomer, although we have not yet proven which.…”

Recent strategies and tactics for the enantioselective total syntheses of cyclolignan natural products

“…Though syntheses of racemic galbulin have been previously achieved, most recently by Whitby 131 and Charlton, 78 Hong and coworkers described the first enantioselective total synthesis of (+)-galbulin ( 121 ) using an organocatalytic tandem double conjugate addition-aldol condensation cascade in 2012. 23 Their synthetic strategy, as illustrated through pathway E in Fig.…”

Efficient Total Synthesis of (±)-Isoguaiacin and (±)-Isogalbulin

“…Some of these syntheses involve the conversion of other natural products 4,11,12 and typically provide aryltetralins in low overall yields and as mixtures of stereoisomers. 13,14 Whitby et al reported the synthesis of (±)-2 using zirconium chemistry in 21% overall yield, 15 and Wang et al successfully produced (±)-2, albeit in a lengthy, nonselective synthesis of 12 steps, 16 while the first enantioselective syntheses of (+)-2 was reported by Xie et al, in 10 steps utilising a Sharpless epoxidation as the enantiodetermining step. 17 During the course of our investigation into the synthesis of various lignans, [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] we have noted various rearrangement reactions, particularly in the synthesis of tetrahydrofuran natural products.…”