Approaches to the Synthesis of Cytochalasans Part9. A versatile concept leading to all structural types of cytochalasans

Starting from D-glutamic acid ( 5 ), the bicyclic compounds 4a and 4b were synthesized via 17 (Schemes 1 and 2). The reaction leading to 4g and 4h with LiCuPh₂ was not successful. But treatment of the N-protected model lactams 19 , 21 , and 22 with Li₂Cu(CN)Ph₂ gave the amino ketones 24 , 26 , and 27 , respectively (Scheme 3). The desired compound 23 was obtained from 20. Conversion of the unprotected lactams 28 , 31 , and 32 gave the phenyl derivative 34 in excellent yields. Ester 35 was transformed to the α -amino-γ- oxo-acid derivative 36. This conversion opens a novel access to this type of compounds.