Multicomponent approach to the alkaloid-type 2-aza-7-oxabicyclo[4.3.0]nonane framework

N-Allyl 3-endo-amino-7-oxabicyclo[2.2.1]hept-5-ene-2-exo-carboxylic acid has been synthesized and has been employed in a Ugi-5-centre-4-component reaction (U-5C-4CR) with various aldehydes and isocyanides; by employing a mixture of methanol and trifluoroethanol the reaction was completely stereoselective. The resulting products have been employed in an unprecedented ring-opening/ring-closing metathesis process with Ru catalyst, to afford stereochemically defined, polysubstituted cis-fused hexahydrofuro[3,2-b]pyridine derivatives in moderate to good yields. This straightforward procedure allows to assemble in just two synthetic steps natural product-like compounds having the 2-aza-7-oxabicyclo[4.3.0]nonane framework, displayed by various alkaloids.