Optisch aktive 3‐Amino‐2<i>H</i>‐azirine als Bausteine für enantiomerenreine αα‐disubstituierte α‐Aminosäuren: Synthese von Isovalin‐Synthonen und Einbau in ein Trichotoxin‐A‐50‐Segment

Abstract

Optically Active 3‐Amino‐2 H ‐azirines as Synthons for Enantiomerically Pure αα‐Disubstiuted α‐Amino Acids: Syntheses of Isovaline Synthons and a Segment of Trichotoxin A‐50 The synthesis of a novel 3‐amino‐2‐methyl‐2‐[2‐(phenylsulfonyl)ethyl]‐2 H ‐azirine derivative 12 with a chiral substituent at the amino group is described. Chromatographic separation of the diastereoisomer mixture gave pure diastereoisomers which, after an electrochemical cleavage of the phenylsulfonyl group, yielded the ( S )‐ and ( R )‐isovalin (Iva) synthons 13a and 13b , respectively. The absolute configuration of the precursor molecule 12b was established by X‐ray crystallography. The Iva synthons were successfully used in the synthesis of the C‐terminal pentapeptide Z‐Leu‐Aib‐( R )‐Iva‐Gln‐Valol of the peptaibole Trichotoxin A‐50 and its epimer.