LDAP User: Mapping drupal role names to LDAP

I am trying to map drupal roles of a user to organisationalUnitName(OU) attribute in user entry of LDAP directory. The mapping I tried is:

[current-user:roles] -> [ou] (or organisationalUnitName)

However with the above mapping I am getting contraints voilation error with above mapping.
What is is the suggested token value and syntax for extracting drupal role names which can then be mapped to ou attribute in LDAP. Once mapped I can use this ou entry to create dynamic group (using dynlist overlay) using the follwing (example):
memberURL: ldap:///ou=people,o=conjurenet,dc=conjurenet,dc=com??one?(ou=administrator)

My user entries dn is ou=people,o=my company,dc=mycompany,dc=com