FRANKFURT, Jan 3 (Reuters) - German stock exchange operator Deutsche Boerse DB1Gn.DE said it was buying a 5 percent stake in Taiwanese futures exchange TAIFEX for $47 million from Yuanta Financial Holdings Co Ltd 2885.TW . From May, Deutsche Boerse's derivatives business Eurex and TAIFEX plan to list daily futures based on futures and options on the Taiwanese blue-chip index TAIEX, Deutsche Boerse said in a statement on Friday, adding the parties were also in very constructive talks on further joint projects. (Reporting by Maria Sheahan; Editing by Erica Billingham) ((maria.sheahan@thomsonreuters.com)(+49 69 7565 1286)(Reuters Messaging: maria.sheahan.thomsonreuters.com@reuters.net)) Keywords: TAIFEX DEUTSCHEBOERSE/STAKE