.beta.-Isothiureidopropionic acid 3-(Amidinothio)propionic acid 3-(Aminoiminomethyl)thiopropanoic acid 5398-29-8 NSC4453 Propanoic acid, 3-[(aminoiminomethyl)thio]- Propionic acid, 3-(amidinothio)- WLN: QV2SYZUM