2-((tert-Butoxycarbonyl)amino)-3,3-dicyclopropylpropanoic acid

CAS 2272861-72-8

A definite molecular skeleton does not always specify handedness. CAS 2272861-72-8 describes a Boc-protected amino acid with two cyclopropyl side groups but no S or R assignment at its alpha carbon. A patent reports the corresponding acid, ester formation, chiral chromatographic separation, and conversion of the selected S ester into the S acid. The sequence distinguishes making the skeleton from selecting one enantiomer. It also shows why an unspecified name must not silently become an S label. Absence of a label alone does not guarantee an exactly equal mixture in every supplied sample. Connectivity, protection state, and stereochemical composition are separate pieces of identity, and molecular mass alone cannot distinguish enantiomers. Matching those pieces correctly makes a published synthetic route interpretable.