OCH l4, X= NH lj., x= o groups with partial cyclization. Completion of the reaction was carried out by using 4: 1: 2 THF-ethylene glycol-2 N hydrochloric acid at 23 OC for 48 h to afford the desired tetrahydrofuran derivative 10 (Chart 11) in 50-70% yield and, in addition, ca. 20% of the isomeric tetrahydropyran (Rfvalues on silica gel plates using 30% THF in hexane 0.42 and 0.48, respectively). The tetrahydrofuran structure for 10 was clearly ...
