Pyrrolidine alkaloids stachydrine

Two reviews on pyrrolidine alkaloids have appeared in volumes I (7) and VI (2) of this series. At that time, the only alkaloids mentioned were hygrine (1), hygroline (2), cuscohygrine (3), stachydrine (4), and betonicine (5). Carpaine,... 

This section summarises recent work on alkaloids containing the pyrrolidine nucleus. A short review concerning the synthesis of this group has appeared. A variety of Labiatae plants have been screened and some of them have been shown to contain pyrrolidine alkaloids. Cuskhygrine has been found in the roots of three Datura species and stachydrine has been obtained from Capparis spinosa3 The structure of trichostachine (1) Piper trichostachyon) has been elucidated by spectral means and confirmed by synthesis. Ficine (5), an interesting flavonoid alkaloid, has been synthesised. Friedel-Crafts reaction between... 

In the few years since the chapter on the pyrrolidine alkaloids was written they have not been the subject of much additional work. The recent investigations to be described relate to hygrine, hygroline, cuscohygrine, stachydrine, betonicine, and turicine. The structure of carpaine has also been fully elucidated, and this alkaloid has been shown to be a piperidine and not a pyrrolidine alkaloid and hence will be described under the heading The P3addine Alkaloids. ... 

It has been shown that the biogenetic precursor of the pyrrolidine ring in plants is ornithine (8). In Medicago sativa L. the alkaloid stachydrine is stored in the seeds and appears to be actively synthesized only during the period of seed formation. At any rate, plants that are 19 weeks old are incapable of converting ornithine into stachydrine or even proline (9). Feeding the coenzyme pyridoxine together with labeled ornithine to the plant, however, results in the formation of radioactive proline, but no stachydrine is formed (10). The addition of methionine... 

Importance Pro is able to participate in a-helices to a much lower extent than other amino acids. It is thus a helix breaker of particular importance for the structure of proteins. Rotation about the amino peptide bond of proline is especially hindered the correct folding of Pro-containing proteins thus appears to be catalyzed by peptidylprolyl cis-fra/u-isomerases (rotamases, EC 5.2.1.8 see FK-506). On account of its presence in gluten, Pro is involved in the Maillard reaction resulting in the typical bread flavor. The inner salt (betaine) of I, l-dimethyl-P. is a widely distributed pyrrolidine alkaloid in plants, e.g., in woundwort (Stachys spp., stachydrin). 

Pyrrolidine alkaloids a group of Alkaloids (see) with simple structmes. P.a. are either derivatives of proline (e.g. stachydrin and its diastereoisomer, beto-nicin), or they are derived from a Af-methyl-2-alkyl-pyrrolidine (e.g. hygrin and cuskhydrin). The latter occur together with the tropane alkaloid with which they share the same biogenetic precursors, ornithine and acetate. 

Pyrrolidine occurs free in small quantities in tobacco and opium and is related to its mother substance pyrrole (Figure 11.2). To this group belong such alkaloids as hygrine from Erythroxylon coca and stachydrine from Stachys tuberifera (Figure 11.3). 

Some of the early reactions applied to stachydrine (42), although somewhat drastic, pointed to the presence of a dimethylamino grouping and a pyrrolidine nucleus in this alkaloid. Fusion of stachydrine with potassium hydroxide liberated dimethylamine while the vapors from the pyrolysis of this alkaloid gave a characteristic pyrrole test. This assumption of a pyrrolidine nucleus in the base is further confirmed by the above conversion of stachydrine into hygrinic acid. Schulze and Trier considered stachydrine to be the methylbetaine of hygrinic acid (XXIII). At about the same time Engeland, in elaborating his scheme for the isolation of... 

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