Infrared Spectra of 3-Phenyl-2-thiohydantoins of Amino Acids and Their Application to Identification of N-Terminal Groups in Peptides

Infrared Spectra of 3-Phenyl-2-thiohydantoins of Amino Acids

“…All phenylthiohydantoins show absorption in the region from 1425 to 1400 cm.-1 (7). A band of medium intensity has also been found in this region for the present substituted phen-ylthiohydantoins and is given by related model compounds such as thiourea, acetylthiourea, 2-thiohydantoin, and 5-methyl-2-thiohydantoin.…”

“…dissolved in ethyl alcohol and mounted as potassium bromide windows in the manner described previously (7). Such spectra showed better resolution than those of the compounds which were mounted as solids in the potassium bromide window.…”

“…Included are the spectra of thiocarbamyl derivatives (II) of some amino acids obtained instead of the 3-(phenyl-p-azophenyl)-2-thiohydantoins, where ring closure could not he achieved.Spectra were recorded with a Perkin-Elmer Model 21 infrared spectrophotometer equipped with a rock salt prism.The regions from 4000 to 3800 and from 2600 to 1800 cm.-1 were always free from absorption bands and are therefore omitted from the figures. DISCUSSION Phenylthiohydantoin Ring.The following assignments were given to the absorption bands characterizing the different groups of the 3-phenyl-2thiohydantoin ring (7) : 1770 to 1740 cm.-1 1600 cm.-1 1425 to 1400 cm.-1 3300 to 3150 cm.-1 1530 to 1500 cm.-1 Ring C=0 vibrations Phenyl group vibrations C=S vibrations NH vibrations These data hold for most of the nitroand azophenyl-substituted phenylthiohydantoins studied and are in good agreement with those given by Randall and coworkers (9), who examined a number of cyclic diacylimide-type compounds including thiohydantoins.…”

“…The following assignments were given to the absorption bands characterizing the different groups of the 3-phenyl-2thiohydantoin ring (7) : 1770 to 1740 cm.-1 1600 cm.-1 1425 to 1400 cm.-1 3300 to 3150 cm.-1 1530 to 1500 cm.-1 Ring C=0 vibrations Phenyl group vibrations C=S vibrations NH vibrations These data hold for most of the nitroand azophenyl-substituted phenylthiohydantoins studied and are in good agreement with those given by Randall and coworkers (9), who examined a number of cyclic diacylimide-type compounds including thiohydantoins.…”

The INFRARED SPECTRA OF SOME DNP-α-AMINO ACIDS

“…While the IiBr pellet spectra of a large nunlber of the allliilo acids (2, 3), and also of their 3-phenyl-2-thiohpdantoins (4), are reported in the literature, there is little inforillation with regard to the infrared spectra of DNP-derivative^.^ This study was uildertalten to compare the spectra (a) of the DNPderivatives of anlino acids with the spectra of the corresponding free amino acids as given in the literature, (b) of the DNP-derivatives of conlparable L-and D~-aillin0 acids, and (c) of the DNP-derivatives of structurally related acids, to see whether such compounds can be identified by their spectra.…”