Synthesen in der Polymyxin‐Reihe 1. Mitteilung. Synthese eines Pentapeptid‐Fragmentes

The protected pentapeptide formyl‐L‐leucyl‐Nγ‐benzyloxycarbonyl‐L‐α,γ‐diaminobutyryl‐Nγ‐benzyloxycarbonyl‐L‐α,γ‐diaminobutyryl‐L‐threonyl‐Nγ‐benzyloxycarbonyl‐L‐α,γ‐diaminobutyric acid, a sequence which is known to occur in the polymyxins, has been synthesized. Different coupling methods including the azide route lead to the same end product, with the same optical rotation. We therefore believe our pentapeptide to be optically pure.