Cantharis vesicatoria

Cantharidin is obtained from cantharides, the dried beetle Cantharis vesicatoria ( = Lytta vesicatoria) (Meloidae) or other spp., containing not less than 0.6%, or from mylabris, the dried beetles Mylabris sidae = M. phalerata), M. cichorii and M. pustulata (Meloidae), containing not less than 1%,... 

Spanish fly Cantharis vesicatoria. Allegedly aphrodisiac. Active component - cantharadin. Encountered also as the powdered insect. Effects blistering of skin and corrosive effect on mouth, abdominal pain, vomiting, diarrhoea, blood passed in vomit and urine. Early increase in WBC. Severe illness recovery likely but deaths recorded. Lethal dose 60 mg cantharadin, 162 mg Spanish fly. 

Cantharides. Spanish fly blistering fly hlistering beetle Cantharis vesicatoria. Habit. Southern and Central Europe, mainly upon Oleaceae and Caprifotiaceae. Constit. 0.6-1% cantharidin, 10-15% fat resinous substances, acetic and uric acids. Powerful irritant, vesicant, rubefacient. Review Ude, Heeger, Pharm. Zentrulhatle 82, 193 (1941). 

Cantharidin is a powerfiil vesicant that can be isolated from dried beetles Cantharis vesicatoria, or Spanish fly ). Outlined here is the stereospecific synthesis of cantharidin reported by Gilbert Stork (Columbia University). Supply the missing reagents (a)-(n). 

Q 15. Explain why the following [4 + 2] cycloaddition reaction does not occur to produce cantharidin isolated from dried beetles Cantharis vesicatoria). 

Cantharidin a toxic agent, M, 196.21, m.p. 218°C, produced by the beetle Cantharis vesicatoria (Spanish fly, blistering beetle), native to southern and central Europe. C. is biosynthesized from mevalonic acid. Its use as an aphrodisiac has caused fatalities. 

The powdered bodies of Mylabris mongolica, when extracted under alkali (not NH3) conditions afforded cantharidinimide (120), and the same substance was also isolated from cantharis (Lytta vesicatoria) (112). The IR spectrum showed bands at 1760, 1710, and 1698 cm 1, the mass spectrum displayed an M+ at m/z 195, and the H NMR spectrum indicated the high symmetry of the isolate, showing a six-proton singlet at 1.25 ppm and a two-proton multiplet at 4.65 ppm for the oxymethine protons. 

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