2.3.3 Isopilosine
Synonyms Carpiline; Carpidine; Pilosine (this compound was originally called pilosine i.e., the cis-isomer of isopilosine.
Biological Source It is obtained from the dried leaflets of Pilocarpus microphyllus (Rutaceae), which has the total alkaloidal content (0.5-1.%) that consists principally pilocarpine along with small portion of isopilosine, pilosine and related structures.
Chemical Structure
[3S-[3α (S*), 4β]]-Dihydro-3-(hydroxyphenylmethyl)-4-[(1-methyl-1H-imidazol-5-yl) methyl]-2 (3H)-furanone. (C16H18N2O3).
Isolation It is isolated from the leaves of P. microphyllus Stapf. (Rutaceae) by adopting standard procedures.*
Characteristic Features
1. It is obtained as needles from ethanol mp 182-182.5°C.
2. Its specific rotation [α ]D20 + 839o ethanol; uvmax (ethanol) : 210 nm (log € 4.10).
Biosynthesis of Imidazole Alkaloids L-Histidine, an amino acid contains an imidazole ring; and is, therefore, the most probable precursor of alkaloids containing this ring system. The imidazole alkaloids usually found in Jaborandi leaves (P. microphyllus and P. jaborandi; Rutaceae) are most likely derived from histidine; however, sufficient experimental data are lacking. Interestingly, the additional carbon atoms may originate from acetate or supposedly from threonine in the case of pilocarpine, whereas pilosine incorporates a phenylpropane C6H3 unit as shown below.
