Stereoselective one-pot syntheses of trans-3-amino-β-lactams from zinc enolates of N-protected α-aminoacid esters and imines.

✍ Scribed by Fred H van der Steen; Johann T.B.H Jastrzebski; Gerard van Koten

• Publisher: Elsevier Science
• Year: 1988
• Tongue: French
• Weight: 262 KB
• Volume: 29
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)87909-5

✦ Synopsis

A new one-pot synthesis of 3-amino-g-lactams that is based on the condensation of simple imines with zinc enolates of disilyl protected glycine esters is mported Isolated yields are high and a rranr-selectivity is observed.

with imines.

With N-(benzylidene)-trimethylsilylamine the ring-closure to fi-lactam does not take place when warming up to mom temperature, but requires additional heating (30 min, 50 "C). We do not yet fully understand, why this is the case for this particular imine.

We believe that the tranr-stereoselectivity of our synthetic route results from a rigid cyclic chairlike transition-state of a Zenolate with an E-imine.

Preliminary studies 1 6 on the st.ructures of a-aminoacid ester enolates show that, as a consequence of intramolecular coonlination of the nitrogen atom, the enolate anion is &elate bonded to the metal centm, thus fixing the Zgeometry around the central double bond. Additional studies concerning the scope of the presented procedure, elucidation of the mechanism, structures of the i&rmediate enolates, etc. are underway.