an N-acyl-D-glucosamine <=> an N-acyl-D-mannosamine
an n-acyl-d-glucosamine <=> an n-acyl-d-mannosamine
an N-acyl-D-glucosamine <=> an N-acyl-D-mannosamine
an n-acyl-d-glucosamine <=> an n-acyl-d-mannosamine