7- perhydro pyrazine methylation

Pyrazinecarboxylic acid gave l-benzyl-4-methyl-6-[C-(pyrazin-2-yl)for-mamido]perhydro-1,4-diazepine (41) (1 -benzyl-4-methylperhydro-1,4-di-... 

The different molecular shapes of diastereoisomeric diketopiperazines allows their ready separation on GLC columns. Whereas with most monocyclic diketopiperazines the dl compounds have shorter retention times than the ll isomers, the reverse is true for perhydro-1,4-dioxopyrrolo[l,2-a]pyrazines. The high degree of diastereoisomeric resolution of these compounds has been studied on a variety of columns. As diastereoisomeric diketopiperazines are more readily separated and studied as their iV-methyl derivatives, GLC and PMR data have been collected for cyclo-L-prolylsarcosine. ... 

Workers at Sandoz have prepared a series of perhydro-1,4-dioxopyrrolo[l,2-a]pyrazines in high yield using the methyl esters of iV-prolylamino acids. " " These esters (128) were obtained by hyd-rogenolysis of the N-benzyloxycarbonyl derivatives (127) over palladium in either acetic acid alone or admixed with ethylacetate. The cyclized products are formed by heating the filtered reaction mixture or by evaporation of the solution followed by heating the residue in vacuo. 

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