En-route to scarce furo[3,2-f]indolizidines, -indolizidin-9-ols and their stable quaternary ammonium salts based on the stereoselective catalytic hydrogenation of furan nucleus

Catalytic hydrogenation of enantiopure furo[3,2-f]indolizin-6(4H)-one 12, furo[3,2-f]-indolizidine 13 and furo[3,2-f]-indolizidin-9-ol 14 accessible in few steps was studied. High diastereoselectivity was obtained with Rh/Al2O3 for 13 and 14 due to haptophilic effect of both OH and CO groups present in these compounds. In addition, the quaternisation of furo-fused compounds and THF-fused derivatives provided ammonium salts in trans- and cis-relationship, respectively.