Biomimetic Construction of the Hydroquinoline Ring System. Diastereodivergent Enantioselective Synthesis of 2,5-Disubstituted <i>cis</i>-Decahydroquinolines
The straightforward enantioselective construction of the hydroquinoline ringsystemfrom 1,5-polycarbonyl derivatives, using (R)-phenyglycinol as a chiral latent form of ammonia, is reported. The process mimics the key steps believed to occur in nature in the biosynthesis of amphibian decahydroquinoline alkaloids. Diastereodivergent routes to enantiopure cis-2,5-disubstituted decahydroquinolines, including
1–2 equivalents of water can be performed efficiently by using RuH2(PPh3)4 catalyst to give the corresponding amides. Under the similar reaction conditions, δ-ketonitriles can be converted into the corresponding ene-lactams, which are versatile synthetic intermediates. The efficiency of the reaction is demonstrated by the short-step synthesis of (−)-pumiliotoxin C.