The amount of points in the star actually wasn't regulated until some year in the mid 1800s which I have forgotten, they even had versions with seven or eight points. However, the five pointed star has always been used in the Imperial Standard and replaced all other versions with the Turkish Republic being founded. There was no "real" Ottoman flag during the Napoleonic Wars because it was not regulated after all.
The number of Ottoman flag-types is absolutely ENORMOUS, however there are NO English or German sources known to me giving details on the use of a six-pointed star in the landforces. That does not mean it wasn't used though.
However merchants used a six-pointed star during the 1800s.