preferred_name: an S-substituted L-cysteine = a thiol + 2-aminoprop-2-enoate
preferred_name_lc: an s-substituted l-cysteine = a thiol + 2-aminoprop-2-enoate
label: an S-substituted L-cysteine = a thiol + 2-aminoprop-2-enoate
label_lc: an s-substituted l-cysteine = a thiol + 2-aminoprop-2-enoate