Catalyzes the attachment of 4-epi-vancosamine from a TDP donor to the beta-OH-Tyr-6 of the aglycone cosubstrate in the biosynthesis of glycopeptide antibiotic chloroeremomycin, a member of the vancomycin group of antibiotics. Strongly prefers devancoaminyl-vancomycin (DVV) as substrate rather than the heptapeptide vancomycin aglycone (AGV). Acts downstream of GtfB. devancoaminyl-vancomycin + dTDP-beta-L-4-epi-vancosamine = chloroorienticin B + dTDP + H(+) Antibiotic biosynthesis; vancomycin biosynthesis. In A.orientalis different glycosyltransferases are involved in biosynthesis of the vancomycin group of antibiotics. GtfA, GtfB (AC P96559) and GtfC (AC P96560) are involved in biosynthesis of antibiotic chloroeremomycin, while GtfD (AC Q9AFC7) and GtfE (AC G4V4R9) are involved in biosynthesis of vancomycin. Belongs to the glycosyltransferase 28 family.