Hello Wladimir.
Almost all of case insensitive searches in SAP CRM are done using dedicated "search" field (we're talking about classical DBs and not HANA and its capabilities). Which represents the desired field in uppercase in the same database table. Compare BUT000-NAME_LAST and BUT000-MC_NAME1, ADR6-SMTP_ADDR and ADR6-SMTP_SRCH fields pairs for example. So your description field should be programmatically converted to upper case and stored in another field. On which you should do the search.
Otherewise you should do a complete scan of database entries and compare pairs converted to the same case.