Cut cake horizontally into 3 even layers.
Use a serrated or bread knife in a back and for the slicing motion while turning the cake for best cutting results.
Combine sour cream, coconut, brown sugar, crushed pineapple, cool whip and orange extract.
Place bottom layer of cake on serving plate; top with one-third of the pineapple mixture.
Add second layer of cake; top with another one-third of pineapple mixture.
Top with final cake layer and spread with remaining pineapple mixture.
Arrange mandarin orange sections around the top and chill thoroughly.
Keep refrigerated, serve cold.