Norsecurinine

Securinega virosa (Roxb.) Pax Hoffmann Bai Yin Shu (leaf, root) Virosine, norsecurinine, dihydrosecurinine, virosecurinin, viroallosecurinine, norsecurinine, fluggein.56 Leaves used as a maturative, a detergent, it has antibiotic activity. Root to treat teeth and gum disease. 

From the family Euphorbiaceae, Phyllanthus niruri L. yielded the new alkaloid nirurine (105) in addition to the former reported occurrence of 4-methoxynorsecurinine and norsecurinine in the same plant (115,116). The structure of (105) was elucidated by analysis of spectral data and X-ray crystallography (117). The pyrrolizidine alkaloid phalaenopsine La (106)... 

This reaction has been utilized in the context of natural product synthesis. A recent example is the synthesis of colletodiol by Keck, shown in equation (45). In this example, no problems were encountoed with epimerization or ester cleavage. The desireid ( )-ester (182) was synttesized in 80% yield. Two examples are outlined (in equations 46 and 47) in which epimerization was a substantial problem with sodium or potassium salts, while the LiCl/amine method effectively suppressed this side reaction. When the phosphonate was allowed to react with the cyclohexanal derivative (183), the sodium salt gave epi-merized material. Use of LiCl and diisopropylethylamine gave an 88% yield of alkene (184), free of epimer (equation 46). In the synthesis of norsecurinine, Heathcock found that the phosphonate anion... 

Scheme 26. Determination of the skeletal structure of norsecurinine (164) by Saito et al. (62).

Reduction of norsecurinine with zinc and suKuric acid gave the oily lactam 169 which was extremely unstable and thus was immediately converted into the hexahydropyrrolo[2,l-a]isoquinoUne 170. This rearrangement was predicted from the previous results of the same reaction effected on securinine and related alkaloids e.g., Section II, A, 1) and was confirmed by synthesis of compound 170 from the pyrrolidinone 171 in two steps. Thus the skeletal structure 164 of norsecurinine as originally proposed (60) was fully confirmed (62). 

Rouffiac and Parello 64) isolated from Phyllanthus niruri L. an alkaloid as yet unnamed whose NMR and mass spectra are identical with those of norsecurinine (Section III, A) and to which solely on the basis of physical and spectral data has been assigned the optical antipode structure of norsecurinine (164a). 

Saito and co-workers isolated an alkaloid from the roots of Securinega virosa which they originally called virosine 53). It was later renamed dihydronorsecurinine to avoid confusion (see footnote e, in Table I) 61). Dihydronorsecurinine was shown to be identical with the sodium borohydride reduction product of norsecurinine (Section III, A). Since the absolute configuration of the latter has been established, the structure and absolute stereochemistry of dihydronorsecurinine is fully represented by formula 165a (Scheme 27) 62). 

Scheme 32. Amide oxidation via 1,5-hydrogen transfer toward the synthesis of (-)-norsecurinine...

Jacobi s group cyclodehydrated iV-carbobenzyloxy-D-prolyl-L-alanine methyl ester 438 using POCVpyridine to prepare large quantities (50 g) of the 5-methoxy-4-methyl-2-substituted oxazole 439 (Scheme 1.121). Both 439 and ent-439 were key starting points for their enantiospecific syntheses of (+)-norsecurinine and (—)-norsecurinine. 

Synthesis of Evodone Synthesis of Ligularone and Petasalbine Synthesis of Paniculide-A Synthesis of Gnididione Synthesis of Norsecurinine Synthetic Approach to Geigerin Synthesis of Stemoamide Thiofurans and Amidofurans... 

Norsecurinine, a member of the Securinega class of alkaloids, occurs naturally in both enantiomeric forms. Jacobi and co-wrokers" " fashioned enantiospecific syntheses of both antipodes starting from either d- or L-proline. 

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