7,8-Dehydrocalotropin Card-20(22)-enolide, 7,8-dihydro-14-hydroxy-19-oxo-2,3-[[(2S,3S,4S,6R)- tetrahydro-3,4-dihydroxy-6-methyl-2H-pyran- 3,2-diyl]bis(oxy)]-, (2.alpha.,3.beta.,5.alpha.)- NSC688285