The Use of the O-Nitrocinnamoyl Group as an Amine Blocking Function

Abstract The thiomethylene oxazolone I is, in principle, a useful synthon for the preparation of 2-substituted cystein derivatives II. However, the benzamide group cannot be removed easily in the presence of other sensitive functionalities. Since compounds of type I have only been described when the substituent at C-2 is phenyl,1 and since there is no reason to believe that compounds of type I with an aliphatic substituent at C-2 are very stable, we thought that the o-nitrocinnamoyl group might be a suitable substituent because of its aromatic character and its similarity to the o-nitrophenoxyacetic group, which has been successfully used as an easily removable amine blocking function.2 We therefore prepared o-nitrocinnamoyl glycine III and converted it via the ethoxymethylene derivative IVa to the sodium salt of the 4-thiomethylene derivative IVb, which is a stable compound.