Crystal structure of the antibiotic SY-1 (20-deoxy-salinomycin): sodium 2-(6-[2- (5-ethyl-5-hydroxy-6-methyl-tetrahydro-pyran-2-yl)-2,10,12-trimethyl- 1,6,8-trioxa-dispiro[4.1.5.3]pentadec-13-en-9-yl]-2-hydroxy-1,3-dimethyl-4-oxo-heptyl-5-methyl-tetrahydro-pyran-2-yl)-butyrate—methanol solvate (1:0.69), C42H69NaO10 · 0.69CH3OH