Synthesis of scopin acetate and 6,7-didehydrohyoscyamin. Intramolecular phenylsulfenylation of a nonactivated methylene group of ethyl N-demethyl-3-O-(phenylthio)tropine-N-carboxylate
The synthesis of scopin acetate (6b) and 6,7-didehydrohyoscyamine (17) was achieved by using tropine (5) as the starting compound. Formal (phenylthio)-radical transfer to the nonactivated 6-position of ethyl N-demethyl-3-O-(phenylthio)tropine-N-carboxylate (9) by irradiation in the presence of hexabutyldistannane is a key step of this synthetic approach, involving ethyl 6,7-didehydro-N-demethyltropine-N-carboxylate (15) as a synthetic intermediate (Schemes 3 and 5). The reaction of 9 with tributylstannane in the presence of ethyl acrylate, as a radicophilic olefin, involves Michael-type alkylation at C(6) of the tropine skeleton affording ethyl N-demethyl-N-(ethoxycarbonyl)tropine-6-propanoate (18) (Scheme 6).
Petrovi?, Goran B.,Sai?i?, Radomir N.,?ekovi?, ?ivorad M.
p. 3179 - 3186
(2007/10/03)
Synthesis of acetyl scopine. Intramolecular reactions of N-carbethoxy nortropine-3α-benzene-sulfenate
The synthesis of acetyl scopine using tropine as a starting compound was achieved. Free radical phenylthio group transfer to the 6-position, in the reaction of N-carbethoxy nortropine-3α-benzenesulfenate with hexabutylditin, is a key step of this synthetic approach to scopine. The reaction of N- carbethoxy nortropine-benzenesulfenate with tributyltin hydride in the presence of a radicophilic olefin involves Michael type alkylation at the 6- position of tropine skeleton affording 6-(2-carbethoxyethyl)-N-carbethoxy nortropine in 31% yield.