hide
Free keywords:
DIELS-ALDER REACTIONS; AQUEOUS-SOLUTION; CYCLOCONDENSATION; PIPERIDINE;
ALKALOIDS; DIENESChemistry;
Abstract:
In the presence of various Lewis acids, the amino acid ester-imines 1 undergo tandem Mannich-Michael reactions and aza-Diels-Alder reactions respectively with the Danishefsky diene 2 and the Brassard diene 3. The products are formed in good yields and high diastereomeric excesses. Cleavage of the chiral auxiliary group-achieved by means of a Curtius rearrangement, by which the alpha-C of the amino acid is converted into an aminal-and subsequent hydrolysis afforded unsaturated lactams such as 4 and enaminones 5, which find use as synthetic building blocks.
