Novel glycopeptide derivatives

A compound of formula (I):

• ##STR11## wherein R is hydrogen or methyl;
• n is 1 or 2;
• and
• (i) R.sub.1 is hydrogen or methyl;
• R.sub.2 and R.sub.3, independently, are hydrogen or a group of the formula:
• R.sub.6 R.sub.7 CH--;
• R.sub.6 and R.sub.7 are independently R.sub.5, R.sub.5 --(C.sub.1 -C.sub.5 -alkyl) or R.sub.5 --(C.sub.2 -C.sub.5 -alkenyl);
• R.sub.5 is hydrogen, C.sub.1 -C.sub.10 -alkyl, C.sub.2 -C.sub.10 -alkenyl, C.sub.1 -C.sub.4 alkoxy, C.sub.3 -C.sub.10 -cycloalkyl, C.sub.5 -C.sub.12 -cycloalkenyl, phenyl, naphththyl, indenyl, tetralinyl, decalinyl, adamantyl, a monocyclic heterocyclic ring system comprising 3 to 8 atoms in the ring or a bicyclic heterocyclic ring system comprising 6 to 11 atoms, provided that at least one atom of the ring system is carbon and at least one atom of the ring system is a heteroatom selected from O, N and S, and R.sub.5 may be substituted with one or more hydroxy, nitro, C.sub.1 -C.sub.10 -alkoxy, C.sub.1 -C.sub.10 alkyl, phenyl, C.sub.1 -C.sub.6 -alkylthio, nitrile, halo, C.sub.2 -C.sub.4 acylamino, amino, C.sub.1 -C.sub.4 dialkylamino groups;
• and
• R.sub.4 is hydrogen;
• or
• (ii) R.sub.1 and R.sub.2 and/or R.sub.3 and R.sub.4 together form a group of the formula ##STR12## provided that:
• (1) at least one of R.sub.2 and R.sub.3 must be other than hydrogen;
• (2) when n is 2, R must be hydrogen;
• (3) when R is methyl and R.sub.3 is hydrogen, R.sub.2 cannot be methyl and (4) when R and R.sub.1 are both methyl, then R.sub.2 is hydrogen or methyl and n is 1;
• or a salt thereof.