| abstract |
A compound of formula I ** Formula ** in which R1 represents (C1-C6) alkoxy; Y represents a bond and Z represents hydrogen; or Y represents (C1-C3) alkanyl and Z represents hydrogen, hydroxy, -COOH, -COOR5, -P (O) (OH) 2, -P (O) (OR6) 2, - P (O) (NHR7) 2 or phenyl, in which phenyl is substituted with -P (O) (OH) 2 or -P (O) (OR8) 2; W represents a group selected from ** Formula ** |