Asymmetric Synthesis of α,β-Epoxy-?-lactams through Tandem Darzens/Hemiaminalization Reaction
A catalytic asymmetric tandem Darzens/hemiaminalization reaction of glyoxals with α-bromo-β-esteramides or α-bromo-β-ketoamide was accomplished in the presence of a chiral N,N′-dioxide/Yb(III) complex. Various chiral α,β-epoxy-?-lactams were obtained in moderate to good yields with excellent diastereo- and enantioselectivities. The versatility of the transformation is illustrated in the formal synthesis of berkeleyamide D.
Short synthesis of berkeleyamide D and determination of the absolute configuration by the vibrational circular dichroism exciton chirality method
The first synthesis of (±)-berkeleyamide D has been accomplished. The key features of this synthesis include the formation of an α,β-epoxy-γ-lactam via a Darzens reaction and the construction of a spirocyclic ring system by a C-acylation reaction followed by an intramolecular spirocyclization via an epoxide-opening reaction. Following optical resolution by chiral HPLC, the absolute configurations of both enantiomers of berkeleyamide D were determined by the vibrational circular dichroism exciton chirality method.