Reversing one or more of the amide groups (ie -CHRCONH- to -CHRNHCO-) of a linear peptide gives a so called 'partially modified retro isomer' and represents an important strategy in peptide analogue research. la92 The modified sequence requires both a malonic unit and an (much less easily available) a,&-diamino moiety. Such &,a-diamino units have been synthesized by Curtius-'J,5 or Hoffmann- t~pe2.3,~ rearrangement of appropriately protected amino acid
