Retronecine hydrochloride

Retronecine hydrochloride, CiHuNOi-HCl. The aqueous solution obtained after ether extraction of monocrotic acid was evaporated to dryness in vacuo. The sirup thus obtained was dissolved in 100 cc. of absolute ethanol and the solvent was removed by evaporation. A crystalline mass resulted and this was extracted with three 30-cc. portions of boiling absolute ethanol to separate the alkaloid salt from barium salts. The combined ethanolic extracts were concentrated to 20 cc. and allow ed to cool. The salt, retronecine hydrochloride, separated and the filtrate yielded an additional amount by the addition of ether. Recrystallization from absolute ethanol gave white prisms, m.p. 161-162° yield, 10.3 g. (87%). 

Direct evidence for the involvement of a symmetrical dimeric intermediate in retronecine biosynthesis was obtained by Khan and Robins (755). They fed [1-ammu- N l- C]-putrescine to S, isatideus plants. The n.m.r. spectrum of the retronecine hydrochloride obtained showed enrichment factors of 0.4—0.5% for the signals at C-3, C-5, C-8, and C-9. In addition, the presence of species was evident from the presence of... 

Many esters, both naturally occurring and semisynthetic, have been prepared by esterification of hydroxy-substituted pyrrolizidine bases. Mattocks synthesized a range of retronecine diesters by heating retronecine (127) hydrochloride with acid chlorides.Mattocks also converted retronecine into the corresponding amine, retronamine, from which amide analogs of pyrrolizidine esters were prepared [Eq. (35)]. 

Platynecine (III), C8H15NO2, first obtained by Orekhov and Tiedebel (38) on alkaline hydrolysis of platyphylline (from Senecio platyphyllus), was degraded to heliotridane by Konovalova and Orekhov (40). The method was as follows Dichloroplatynecine, CgHisChN, m.p. 63-64° (hydrochloride, m.p. 186-187° picrate, m.p. 205-206°) was obtained in low yield when platynecine was treated with thionyl chloride. When dichloroplatynecine was reduced with sodium and ethanol followed by hydrogen over platinum oxide catalyst, heliotridane was the product. Identity was established by specific rotation and mixed melting points of all derivatives (54). The formation of heliotridane from platynecine proved that this alkaloid hydrolysis product also has the same basic skeleton that is present in heliotridine and retronecine. 

The position of the ethylenic linkage at to C or C to C has been dealt with by Adams and Mahan. When monocrotaline is catalytically hydrogenated until one molecule of hydrogen has been absorbed, the normal basic hydrolytic product retronecanol (VIII) is replaced by deoxyretronecine (XII), CgHjgON, m.p. 77-8°, which forms a hydrochloride, m.p. 182-3°, [ ]d —15-9° (HgO), and a picrate, m.p. 157-8°, and on further hydrogenation yields retronecanol (VIII) from which it differs by retaining the ethylenic linkage of the retronecine residue in monocrotaline. With thionyl chloride deoxyretronecine hydrochloride is... 

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