Catalyzes the attachment of dTDP-L-4-epi-vancosamine to chloroorienticin B to form chloroeremomycin in the biosynthesis of glycopeptide antibiotic chloroeremomycin, a member of the vancomycin group of antibiotics. Also able to use dTDP-L-4-epi-vancosamine and devancoaminyl-vancomycin (DVV) to create epivancomycin. Acts downstream of GtfA. devancoaminyl-vancomycin + dTDP-beta-L-vancosamine = dTDP + epivancomycin + H(+) chloroorienticin B + dTDP-beta-L-vancosamine = chloroeremomycin + dTDP + H(+) Antibiotic biosynthesis; vancomycin biosynthesis. In A.orientalis different glycosyltransferases are involved in biosynthesis of the vancomycin group of antibiotics. GtfA (AC P96558), GtfB (AC P96559) and GtfC 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.