of the formula v str6 in which a e e and b have the abovementioned meaning and the resulting compounds subsequently step 2 being alkylated to form compounds of the formula i or which comprises the compounds of the formula iv being alkylated and the resulting compounds subsequently being cyclized with activated carbonic acid derivatives or oxalic acid derivatives to form compounds of the formula i the reaction is effected in accordance with methods known to the person skilled in the art e g j march 34 advanced organic chemistry 34 3rd ed wiley interscience new york 1985 synthesis of the compounds of the formula iv has been described e g a peyman et al angew chem 105 1993 1852 b stowasset etal tetrahedron lett 33 1992 6625 in step 1 reagents of the formula x c u2550 l x 39 are employed for synthesizing the cyclic ureas where x and x 39 are leaving groups and l is defined as above the reaction is carried out under increased dilution in order to make the ring closure possible examples of x c u2550 l x 39 are carbonyldiimidazole thiocarbonyldiimidazole phosgene thiophosgene diphenyl carbonate diphenyl thiocarbonate and bistrichloromethyl carbonate activated derivatives of oxalic acid preferably oxalyl chloride are employed under the above mentioned conditions for synthesizing cyclic oxalic acid diamides where appropriate functional groups not however the terminal amino groups in the diamines iv are protected by methods known to the person skilled in the art e g greene wuts 34 protective groups in organic synthesis 34 j wiley new york 1991 for example hydroxyl groups are protected with acyl groups such as acetyl or phosphinic acids are protected where appropriate as esters such as methyl esters in step 2 the compounds of the formula v.