Modifying SQL Server Synonyms (Can't Alter Synonyms)

DECLARE
    @DropSynonym NVARCHAR(4000),
    @CreateSynonym NVARCHAR(4000),
    @Permissions NVARCHAR(4000)

SELECT
    @DropSynonym = '',
    @CreateSynonym = '',
    @Permissions = ''

SELECT
    @DropSynonym = @DropSynonym + 'DROP SYNONYM '
    + QUOTENAME(SCHEMA_NAME(SCHEMA_ID)) + '.' + QUOTENAME(NAME) + ';
',
    @CreateSynonym = @CreateSynonym + 'CREATE SYNONYM '
    + QUOTENAME(SCHEMA_NAME(SCHEMA_ID)) + '.' + QUOTENAME(NAME) + ' FOR '
    + REPLACE(base_object_name, '[OldDB]', '[NewDB]') + ';
'
FROM
    sys.synonyms ;
WITH    PermQuery
          AS (SELECT
                CASE WHEN perm.state <> 'W' THEN perm.state_desc
                     ELSE 'GRANT'
                END COLLATE database_default AS PermissionState,
                perm.permission_name COLLATE database_default AS Permission,
                SCHEMA_NAME(obj.schema_id) AS SchemaName,
                obj.name AS ObjectName,
                CASE WHEN cl.column_id IS NULL THEN SPACE(0)
                     ELSE '(' + QUOTENAME(cl.name) + ')'
                END AS ColumnName,
                CASE WHEN perm.state <> 'W' THEN 'N'
                     ELSE 'Y'
                END AS WithOption,
                usr.name AS UserName
              FROM
                sys.synonyms AS s
                INNER JOIN sys.all_objects AS obj
                    ON s.object_id = obj.object_id
                INNER JOIN sys.database_permissions AS perm
                    ON perm.major_id = obj.[object_id]
                INNER JOIN sys.database_principals AS usr
                    ON perm.grantee_principal_id = usr.principal_id
                LEFT JOIN sys.columns AS cl
                    ON cl.column_id = perm.minor_id
                       AND cl.[object_id] = perm.major_id)
    SELECT
        @Permissions = @Permissions + PermissionState + ' ' + Permission
        + ' ON ' + QUOTENAME(SchemaName) + '.' + QUOTENAME(ObjectName) + ' '
        + ColumnName + ' TO ' + UserName
        + CASE WithOption
            WHEN 'Y' THEN ' WITH GRANT OPTION'
            ELSE ''
          END + ';
'
    FROM
        PermQuery

PRINT @DropSynonym
EXEC(@DropSynonym)

PRINT @CreateSynonym
EXEC(@CreateSynonym)

PRINT @Permissions
EXEC (@Permissions)