the sodium salt of glutamic acid. In that case, the reductive alkylation can be realized in methanol by using a triethylammonium salt. The uses of 2 molar equivalent of triethylammonium salt of glutamic acid for one molar equivalent of aldehyde strongly raise the yields. Cyclization of the N-substituted glutamic acids obtained gives then N-arylmethyl pyroglutamicacids in good yields.
Studies on pyrrolidinones: a reaction of methylene dichloride under Friedel–Crafts conditions. Synthesis of an α-hydroxymethyl ketone in the hexahydrobenzo[f]indolizine series
When carried out in methylene dichloride, the Friedel–Crafts cyclization of N-arylmethyl pyroglutamates can lead to addition of a CH2OH group in the position α to the newly formed ketone function.