preferred_name: an N-acyl-D-glucosamine <=> an N-acyl-D-mannosamine
preferred_name_lc: an n-acyl-d-glucosamine <=> an n-acyl-d-mannosamine
label: an N-acyl-D-glucosamine <=> an N-acyl-D-mannosamine
label_lc: an n-acyl-d-glucosamine <=> an n-acyl-d-mannosamine