ULTRASOUND IN NATURAL-PRODUCTS SYNTHESIS - APPLICATIONS TO THE SYNTHESIS OF HISTRIONICOTOXIN VIA NITROALKANAL ACETALS

Ultrasound promoted the Kornblum reaction of silver nitrite or sodium nitrite with haloalkyl acetals to afford the corresponding C-nitro com pounds. The acetalprotected nitro compounds were used as reactants in a 'double Henry' reaction to produce the key intermediate nitrocyclohe xane diol with a masked aldehyde side chain. The nitrodiol was then su bjected to an ultrasound-promoted one-pot/single operation sequence in volving a reduction-deprotection followed by a cyclization-reduction. The entire sequence provided the core spiropiperidine substructure of the histrionicotoxins. (C) 1997 Elsevier Science B.V.