D-Glucose

D-Glucose Fischer Projection
00:57 - see notes for Haworth cyclization and arrow-pushing
01:03 - see my notes for alpha vs beta glucose and assigning priority to groups
castExc(LowestPriorityGroupOnHorizontal)
return inverted answer
Because the lowest priority group is hydrogen, you can either do this only for carbon 5 or three times for carbons 2-4 and not on carbon 5....