Experiments with Claviceps spec., strain SD 58, showed that L-tryptophan is a more immediate precursor of ergot alkaloids than D-tryptophan. With the exception of the carboxyl group all carbon, nitrogen and hydrogen atoms of the alanine side chain are incorporated into the alkaloids from L-tryptophan. In the case of D-tryptophan the nitrogen and the α-hydrogen of the side chain are lost during incorporation. Degradative studies confirmed that the tritium of DL-tryptophan- [alanine-2 -3H] is transferred to position 5 of the ergoline ring. The results show, that n-tryptophan is converted into the L-form via the keto acid prior to incorporation. The condensation reaction at the α-carbon of the tryptophan side chain during alkaloid biosynthesis probably involves a Waldeninversion. The mechanism of this reaction is discussed.
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