To get some more useful help here, you'll need to provide some more information with your request. What's not working? What are you seeing happen? Log entries etc.
Alfresco subsystem configuration can be a little particular around where property values are placed, in that you need to create a suitable folder structure for Alfresco to look for the properties in. See here for details: http://docs.alfresco.com/4.1/tasks/subsystem-classpath.html
Basically, in your case you need to make sure your properties related to the ldap subsystem go in a properties file related to the right instance of the ldap subsystem (there can be more than one in more complex configurations) e.g. tomcat/shared/classes/alfresco/extension/subsystems/Authentication/ldap/ldap1/mychanges.properties as that's where Alfresco's going to look for the property values for this subsystem.
If this works, great! If not, look at the logs being produced by Alfresco at start up, specifically the ones where it says "Starting 'Authentication' subsystem" … "Startup of 'Authentication' subsystem […..] complete" and "Starting 'Synchronization' subsystem" … "Synchronizing users and groups with user registry 'ldap1'" … "Startup of 'Synchronization' subsystem […] complete"
Setting the log level of org.alfresco.repo.security.sync.ChainingUserRegistrySynchronizer to DEBUG should also give some more clarity around what's happening when the synchronization process starts