Regioselective lithiation and functionalization of 3-(benzyloxy)isothiazole: application to the synthesis of thioibotenic acid |
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Authors: | Bunch Lennart Krogsgaard-Larsen Povl Madsen Ulf |
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Institution: | Department of Medicinal Chemistry, The Royal Danish School of Pharmacy, Universitetsparken 2, DK-2100 Copenhagen, Denmark. |
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Abstract: | Direct functionalization of the 3-oxygenated isothiazole heteroaromatic parental system has not yet been reported in the literature. Here, we report the first regioselective lithiation of the 5-position of 3-(benzyloxy)isothiazole (4) using LDA in diethyl ether. The versatility of the methodology was explored by quenching with a variety of electrophiles to give the desired products 7a,b,d-g in 54-68% yield. Only benzoylation aiming at the synthesis of 7c was unsuccessful. Furthermore, a highly convergent synthesis of thioibotenic acid (1), the sulfur analogue of the neurotoxic natural product ibotenic acid, was carried out. |
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