Some Oxidation Reactions of Delcosine

Abstract

The alkaloid delcosine was oxidized by chromic acid in acetic acid, and also by the Oppenauer reaction, to dehydrodelcosine in which the carbonyl was shown by infrared absorption to be in a pentatomic ring. Oxidation of the alkaloid with silver oxide gave two products: (a) N-desethyldelcosine, which could be N-acetylated or converted back to the original base by ethylation, thus proving the presence of an N-ethyl group; (b) a compound, C24H37O7N, the properties of which agreed best with those of an internal ether, i.e., anhydrohydroxydelcosine. The action of N-bromosuccinimide on the alkaloid produced the same two compounds as silver oxide, plus a derivative, C22H33O7N, that proved to be N-desethyl-anhydrohydroxydelcosine. Potassium permanganate oxidized delcosine to a product, C22H31O7N, that had lost the N-ethyl group, contained the internal ether, and also a carbonyl in a five-membered ring. This same product was obtained on similar oxidation of N-desethyl-anhydrohydroxydelcosine. Oxidation of delcosine with mercuric acetate gave N-desethyldelcosine and N-desethyl-anhydrohydroxydelcosine, together with a compound that was very soluble in water and proved to be the carbinolamine formed by hydroxylation of the methylene in the N-ethyl group. These results are discussed in terms of a structure that is tentatively advanced for delcosine.

The Epimerization of Delcosine

“…I t has been shown earlier (2,3) that delcosine contains a secondary hydroxyl substituted on the six-membered ring A. Oxidation of delcosine with either silver oxide or N-brornosuccinimide gives rise to a carbinolaniine ether, anhydrohydroxydelcosiile I1 (1,3), the forination of which involves this secondary hydroxyl, which was assumed to occupy position C-1 by analogy with lycoctonine. This conclusion is also supported by the results of the oxidation of oxodelcosine with lead tetraacetate (3).…”

“…Sparatore, Greenhalgh, and Marion (6) have attempted this epimerization in delsoline, which is a monon~ethyldelcosil~e ( 2 ) , but their reported result is in error, and the con~pound that they have described is not epidelsoline but Af-anhydrodelsoliile (C?jIlg~OtjN). Dvornik and Edwards (7) reported the epimerization of a hydroxyl in ajaconine, and Dr. Dvornik suggested to us an adaptation of the method by which it has now proved possible to prepare epidelcosiile from N-desethyldelcosine, a previously described oxidation product of the base (1). N-Desethyldelcosine (IV) was oxidized by Sarett's reagent to a mixture of N-desethyl-1,lO-didehydrodelcosine-azomethie (V) and the neutral N-desethyl-1,lO-didehydro-oxodelcosine.…”

“…spectrum, 110 methyl group attached to carbon is present besides that of the N-ethyl group, it becollles highly probable that the third methoxyl in the molecule is present in a methoxy-methyl group a t C-17. Delcosine contains a secondary hydrosyl attached to a five-membered ring (1,3). This hydroxyl has been located a t C-10 by analogy with lycoctonine, which contains a methox~il a t that position, but besides the fact that it nlust be a substituent on ring D, there is no proof of its exact location.…”

The highly-oxygenated diterpenoid alkaloids

“…Further, the Oppenauer oxidation of delcosine gives rise to a mono-ketone, dehydrodelcosine, in which the carbonyl is in a five-membered ring 32 • Consequently, the secondary hydroxyl in the five-membered ring is more readily amenable to reaction than the other. This is also true of acetylation.…”

The Partial Structures of Aconitine and Aconitoline

“…T h a t the ~llethoxyl and l~ydroxyl groups should be as shown in 111, and not in the reversecl positions, is apparent from the fact t h a t the presence of a hydroxyl in position I , provided it has the right orielitation, should on oxidation lead to the formation of an internal ether as i l l delcosine (10) and in delsoline (12) and such an internal ether has not been obtained from aconitine. Consecluently, aconitoline is represented as IV \\rhich is a P-aminoketone.…”