An improved procedure for the preparation of substituted 4-hydroxy-4,5-dihydrofurans

✍ Scribed by Johann Jauch; Volker Schurig

• Publisher: Elsevier Science
• Year: 1991
• Tongue: French
• Weight: 252 KB
• Volume: 32
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)92282-2

✦ Synopsis

LiBr-activated cyclization; natural products NMns& An improved, highly diastereoselective procedure is described for the preparation of substituted 4-hydroxy-4,Sdihydrofurans 4 which are structural elements that occur in azadirachtin and several other biologically active natural products. During our studies towards the synthesis of model compounds for insect antifeedants &ated to the tricyclic hydroxy-dihydrofuran part 1 of azadirachtin' we investigated the reaction of a-hydroxy-ketones' 2 with various esters of acetylenedicarboxylic acid3 3. This transformation has been mentioned in the literature 4-6 for three times, i.e. the reaction of dimethyl acetylenedicarboxylate (39 with benzoin, furoin and acetoin. respectively, giving the racemic substituted 4-hydroxy-4,5-dihydrofurans 4. In our hands, the procedures are very unsatisfactory. Therefore we developed an improved, mild method leading to substituted 4-hydroxy-4,Sdihydrofurans 4.