Nucleophilic additions to (4S)-1-alkylidene-2,4-dihydro-1H-pyrazino[2,1-b]quinazoline-3,6-diones

Investigation of the title compounds as didehydro amino acid templates show ed their lack of reactivity against amines or Grignard reagents under coppe r(I) catalysis, but efficient additions to the exocyclic double bond took p lace with mercaptides or stabilized carbanions. Regio- and diastereoselecti ve addition of organometallic reagents occurred at the C(3)-position and, i n l-methylene derivatives, these reactions were followed by a rearrangement of the intermediate oxy-anion to give pyrido[2, 1-b]quinazolines. (C) 2001 Elsevier Science Ltd. All rights reserved.