A series of non-natural N-acyl derivatives of lactosamine is incubated with recombinant alpha(1-3)galactosyl-transferase and UDP-galactose. The enzyme shows a high promiscuity towards the nonnatural accepters. It selectively transfers a galactose unit onto the 3-OH group of the terminal beta-linked galactose in an alpha-mode to give an array of linear-B trisaccharides. (C) 1998 Elsevier Science Ltd. All rights reserved.