- Synthesis of spiroacetal enol ethers by oxidative activation of furan derivatives
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(Chemical Equation Presented) Activation of furan by electron transfer combines with the radical stabilizing effect of the alkynyl substituent (R = Ph, MeC=C-) to achieve site-selective cation formation. A tethered hydroxy group acts as a probe of this site-selectivity to produce the ring system present in spirocyclic natural products found in Artemisia and Chrysanthemum species. cis-Dihydroxylation proceeds with high anti-stereoselectivity with respect to the tetrahydropyranyl ring oxygen.
- Robertson, Jeremy,Naud, Sebastien
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supporting information; experimental part
p. 5445 - 5448
(2009/06/18)
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- A straightforward synthetic approach to the spiroketal-enol ethers synthesis of natural antifeeding compound tonghaosu and its analogs
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Tonghaosu 1, a natural product discovered from several plants of tribe Athemdeae, is a [4.4]spiroketal with an enediyne side-chain and shows interesting insect antifeeding activity. In this paper a general and convenient synthetic methodology for the synthesis of 1, 2 and its spiroketal-enol ether derivatives is described. Thus, 3-(2'-furyl)-propan-1- ol 7a or 4-(2'-furyl)-butan-1-ol 7b prepared from furaldehyde was treated with n-butyl lithium and unsaturated aldehyde to provide the diol 5. Diol 5 could also be obtained from 5-(3-acetoxypropyl)-2-furaldehyde or 5-(4- acetoxybutyl)-2-furaldehyde and alkynyllithium. By careful treatment of 5 or 7 with acid, dehydration-cyclization occurred to give the desired spiroketal- enol ether in moderate to excellent yields.
- Gao, Yang,Wu, Wen-Lian,Wu, Yu-Lin,Ye, Bin,Zhou, Rong
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p. 12523 - 12538
(2007/10/03)
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