Peptide-hormone analogues.

When is a peptide not a peptide? The ingenuity of the organic chemist is reflected in analogues with less and less resemblance to their parent molecules. Some are barely even recognizable as peptides; one needs a major in chemistry and a good road map to work out exactly what devilment has been inflicted on thyrotropin releasing hormone, for example, to generate pyro-(α-amino adipyl)-histidyl-thiazolidine-4-carboxamide, an analogue with powerful and selective effects on the central nervous system.1 Even the peptide backbone is no longer sacred, since aza-analogues, in which the α carbon atom is replaced by nitrogen, have been synthesized for several . . .