N-y-L-Glutamyl amino-D-proline

Succinimide (22) was transformed into 2-ethoxypyrrolin-5-one (O-ethylsuccinimide) (23) by the action of triethyloxonium tetrafluoroborate. 2-Ethoxypyrrolin-5-one was then transformed photochemically to t-butyl N-(l-ethoxycyclopropyl)carbamate (24). This compound when treated 

Because of the instability of p-hydroxymethylphenylhydrazine (31) all steps in the synthesis had to be carried out under neutral conditions. Condensation of the hydrazine, produced by LiAlH4-reduction 

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