Investigation of the constituents of RyaniaSpeciosa

Abstract

; 2840 (1985). Six new metabolites (2, 5-9) were isolated from the extracts of Ryania Speciosa Vahl. These compounds are closely related to ryanodine, the known insecticidal toxic alkaloid from this plant.Luc RUEST, DAVID R. TAYLOR et PIERRE DESLONCCHAMPS. Can. J. Chem. 63, 2840 (1985). Six nouveaux mktabolites (2, 5-9) ont CtC isolCs des extraits de la plante Ryar~ia Speciosa Vahl. Ces composCs sont Ctroitement reliCs i la ryanodine, un alcaloide toxique connu provenant de cette plante.Although the insecticidal diterpene ester ryanodine (1) (1) has been isolated from Ryarzia Speciosa since 1948 (2), to our knowledge no other diterpene had been reported from this genus prior to 1984. Very recently Waterhouse, Holden, and Casida (3) reported the isolation and characterization of dehydroryanodine (2), the second most abundant toxic (3) alkaloid (besides ryanodine) from Ryania Speciosa. Ryanodine (1) is a complex, highly oxygenated diterpene in which the unrearranged geranyl-geraniol (3) unit is easily discerned as proposed by Wiesner (1). An examination of the constituents of Ryania Speciosa was undertaken to seek compounds related to ryanodine as (i) alternate synthetic targets;' (ii) possible precursors on the biogenetic pathway to ryanodine. The actual growing interestZ in the toxic constituents of Ryania Speciosa prompted us to publish some results obtained some years ago in our laboratory.This report describes the isolation and identification of six diterpene esters of a-pyrrole carboxylic acid closely related to ryanodine (1): the already known (3) dehydroryanodine (2), diterpene esters A (5), B (6), C , (7), C2 (8), and D (9).The structure of dehydroryanodine (2), the major new diterpene slightly more polar than ryanodine (see Experimental), was proven by spectral analysis and by catalytic hydrogenation to a mixture of ryanodine (1) and 9-epiryanodine (10). We will not discuss further the structure of this compound (cf. Experimental for details) since it has been at least partly described in ref. 3.Compounds A, £3, C,, CZ, and D were isolated by chromatography of the crude extracts of powdered stems of Ryania Speciosa (2). 'Their Rf values are all greater than that of ryanodine and they are Iisted in order of increasing polarity, A being the least polar (see Experimental).Spectral data of diterpene ester A (5) are in agreement in all respects with the proposed structure. The mass spectrum indicates a formula of C26H,,010N, which is equivalent to the addition of CHZO to ryanodine, suggesting that ester A has one more hydroxyl group than ryanodine and that one of the hydroxyl groups has been methylated. The structure is supported by nmr spectral analysis: it shows three multiplets from 6.2 to 7.1 6 (for the pyrrole-a-carboxylate moiety), a sharp singlet at 5.68 6 (3-H), a methoxy at 3.56 6, an AB pattern at 2.62 and 1.83 6 (for 14-H2 on the heterocyclic ring), two tertiary and three secondary methyl groups. In addition, after DzO ex-' For a total synthesis of ryanodol (4) see rcf. 4.'At submicromolar concentr...

The total synthesis of (+)-ryanodol. Part IV. Preparation of (+)-ryanodol from (+)-anhydroryanodol

“…The total synthesis of optically active (+)-ryanodol (7) is thus completed. There remains the task of converting (+)-ryanodol (7) into (+)-ryanodine (8).…”

“…Ryanodine (8) was isolated (7,8)4 and converted by basic hydrolysis to (+)-ryanodol (7), which was transformed under acidic conditions into (+)-anhydroryanodol (6) following the procedure described by Wiesner and his collaborators (7).…”

Ryanoids and related compounds. Identification of five new ryanoids from the plantRyaniaspeciosaVahl. Formal total syntheses of 3-deoxyryanodol (cinnzeylanol), 10-O-acetyl-3-deoxyryanodol (cinnzeylanine), 2-deoxyryanodol, 2-deoxy-2-epiryanodol, 2,3-dideoxy-2,3-dihydroryanodol, 2-deoxy-3-epiryanodol, and 2-deoxy-3-epiryanodine

“…Recentlv, we have identified four new rvanoids (3)(4)(5)(6) (Fig. 1) and corrected the structure of a fifth one (7) reported e&lier ~~a n o d i n e (1) (Fig.…”

Chemical Conversion of Ryanodol to Ryanodine

“…Finally, three-step chemoselective deprotection furnished hexaol 1. The new methodology and protection tactics described here will enable generation of chemical derivatives of this exceedingly complex structure [41][42][43][44] and have further application to total syntheses of biologically active natural products with pyrrole esters. [45][46][47] …”