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Notes: On the Carotenoids Flavoxanthin and Chrysanthemaxanthin: 1H-NMR., 13C-NMR. and Mass Spectra, Absolute Configuration, Survey of Published DataVery pure flavoxanthin (1) and chrysanthemaxanthin (2) have been reisolated from flower heads of Taraxacum officinale. Both compounds were characterized by chromatographic, chemical and chiroptical data and extensive NMR. measurements. Examination of many published data on 1 and 2 led to the conclusion that flavoxanthin has often been mistaken for chrysanthemaxanthin and vice versa.Chemical degradation of 1 and 2 to (-)-loliolide (5) coupled with NMR. evidence (ASIS, spin-decoupling, NOE) allowed the assignment of the absolute configurations of 1 and 2. Thus (+)-flavoxanthin is (3S,5R,8R, 3′R,6′R)-5, 8-epoxy-5, 8-dihydro-β, ε-carotene-3, 3′-diol and (+)-chrysanthemaxanthin its C(8)-epimer.

Notes: Leaf-gland pigments from labiatae: structures of 16 diterpenoids (coleons and royleanones) from Coleus coerulescens GÜRKEThe Abyssinian labiate Coleus coerulescens has been investigated for its leaf-gland pigments. From the very complex mixture of abietanoic diterpenoids the following pure constituents were isolated and their structures established: (1)Diosphenols: coleon C (1a), 16-O-acetyl-coleon C (1b), coleon W (1f);(2)A/B-trans-6, 7-diketones: coleon D (2b), 16-O-acetyl-coleon D (2c), coleon V (2a);(3)Spiro-coleons: 7,12-bis(O-desacetyl)-coleon N(3a), 12-O-desacetyl-coleon N (3b), coleon O (4), 6,12-bis (O-desacetyl)-coleon R (5a), 12-O-desacetyl-coleon R (5b), 3-O-desacetyl-3-O-formyl-coleon Y (5g);(4)Royleanones: The abeo-compounds 6a, 6b, and 7.Main compounds are 3b, 5e and 5g. This is the first record of a co-occurrence of diosphenols, 6,7-dioxo-coleons, spiro-coleons and royleanones. Preliminary experiments show that solvolytic opening of the cyclopropane-ring followed by tautomerisation, oxidation to hydroxy-p-benzoquinones or elimination to quinomethanes and subsequent nucleophilic attack of the solvent leads to compounds with a 2′-substituted propyl group at C(13), thus supporting the biosynthesis of the unusual coleon E side chain.

Notes: The Crystal and Molecular Structure of cis-Coleon D, a cis-A/B-6,7-Dioxo Derivative of Abietane.The X-ray analysis of cis-Coleon D (1) confirmed the postulated position of H—C(5) in the plane of the neighbouring keto group. This situation is unfavourable for enolisation, in contrast to the situation where the H—C(5) is perpendicular to the keto plane, as supposed in trans-Coleon D (2). The α-diketone moiety has a significant (P)-helicity of about 10 (1)°. The acentric crystal structure of cis-Coleon D was determined by direct methods and refined with 1533 structure amplitudes to R = 0.042. The absolute configuration was determined from the known chirality of the A/B-ring junction.

Notes: Structures of Six Coleons (Diterpenoids) from Solenostemon monostachys (P. BEAUV.) BRIQ. (Labiatae)The above mentioned African labiate has been investigated for its leaf-gland pigments. Besides the already known coleons C (1) and H (2), 2a-formoxy-coleon C (3), 12β-O-acetyl-coleon Z (7), 12β-O-acetyl-7-O-formyl-7-O-desacetyl-coleon Z (8) and a not separated mixture of 17-acetoxy-12β-O-acetyl-coleon Z (9a) and 12β-O-acetyl-17-formoxy-coleon Z (9b) have been isolated.

Notes: Partial Synthesis of Grandidones A, 7-Epi-A, B, 7-Epi-B, C, D and 7-Epi-D, from 14-HydroxytaxodioneOxydative addition of coleon U (6) to 14-hydroxytaxodione (5) in the presence of Fétizon's reagent mainly leads to grandidone A (1a) and 7-epigrandidone A (1b) (ca. 15:1), whereas coleon V (7) and 5 under the same conditions yield grandidone B (2a) and 7-epigrandidone B (2b) (ca. 3:1). Dimerization of 14-hydroxytaxodione (5) gives grandidone C (3; ca. 40%), grandidone D (4a; ca. 50%) and 7-epigrandidone D (4b; ca. 10%). All these compounds obtained by partial synthesis are in every respect identical with the natural products, thus establishing their absolute configurations. The thermal transformation of grandidone C (3) to grandidone D (4a)/7-epigrandidone D (4b) and interconversions of 4a and 4b were achieved.Oxydative addition of coleon U (6) to 14-hydroxytaxodione (5) in the presence of Fétizon's reagent mainly leads to grandidone A (1a) and 7-epigrandidone A (1b) (ca. 15:1), whereas coleon V (7) and 5 under the same conditions yield grandidone B (2a) and 7-epigrandidone B (2b) (ca. 3:1). Dimerization of 14-hydroxytaxodione (5) gives grandidone C (3; ca. 40%), grandidone D (4a; ca. 50%) and 7-epigrandidone D (4b; ca. 10%). All these compounds obtained by partial synthesis are in every respect identical with the natural products, thus establishing their absolute configurations. The thermal transformation of grandidone C (3) to grandidone D (4a)/7-epigrandidone D (4b) and interconversions of 4a and 4b were achieved.Oxydative addition of coleon U (6) to 14-hydroxytaxodione (5) in the presence of Fétizon's reagent mainly leads to grandidone A (1a) and 7-epigrandidone A (1b) (ca. 15:1), whereas coleon V (7) and 5 under the same conditions yield grandidone B (2a) and 7-epigrandidone B (2b) (ca. 3:1). Dimerization of 14-hydroxytaxodione (5) gives grandidone C (3; ca. 40%), grandidone D (4a; ca. 50%) and 7-epigrandidone D (4b; ca. 10%). All these compounds obtained by partial synthesis are in every respect identical with the natural products, thus establishing their absolute configurations. The thermal transformation of grandidone C (3) to grandidone D (4a)/7-epigrandidone D (4b) and interconversions of 4a and 4b were achieved.Oxydative addition of coleon U (6) to 14-hydroxytaxodione (5) in the presence of Fétizon's reagent mainly leads to grandidone A (1a) and 7-epigrandidone A (1b) (ca. 15:1), whereas coleon V (7) and 5 under the same conditions yield grandidone B (2a) and 7-epigrandidone B (2b) (ca. 3:1). Dimerization of 14-hydroxytaxodione (5) gives grandidone C (3; ca. 40%), grandidone D (4a; ca. 50%) and 7-epigrandidone D (4b; ca. 10%). All these compounds obtained by partial synthesis are in every respect identical with the natural products, thus establishing their absolute configurations. The thermal transformation of grandidone C (3) to grandidone D (4a)/7-epigrandidone D (4b) and interconversions of 4a and 4b were achieved.

Notes: Leaf-gland Pigments from Labiatae: 22 Novel Diterpenoids (Coleons and Royleanones) from Plectranthus lanuginosusWe report the isolation and structure elucidation of 22 novel diterpenoids (named lanugones A, B, C, D, E, F, G, H, I, J, K, K′, L, M, N, O, P, Q, R, S and (155)-coleon C (28) and (155)-coleon D (29)) from the leaf-glands of the above-mentioned plant (see Table 1). Structurally they belong to the subgroups of royleanones and coleons with the following structural characteristics: 8-hydroxy-1-methyl-spi-ro[2,5]oct-5-ene-4,7-diones, p-quinomethanes, extended (vinylogous) quinones, di-osphenols and diketones. Compounds 28 and 29 are (15S)-epimers of the already known coleon C and coleon D (with (15 R)-configuration), respectively. Furthermore, the already known 6,7-didehydroroyleanone (1) has been isolated in small amount.The present investigation has uncovered the broadest range of diverse chromo-phoric systems and oxydation levels so far found amongst diterpenoids in a single plant species. Most important for an understanding of the metabolic fate of an iso-propyl group is the full range found with the following metabolic stages: isopropyl-→ hydroxyisopropyl → dihydrofuran and spirocyclopropane → allyl- and 2-hydroxypropyl groups.

Notes: Natural Occurrence of C(15)-Epimeric Coleons C and D and its Significance to the Stereochemistry of the Formation of a SpirocyclopropanringIn a previous paper some evidence was presented for a predominant occurrence of epimeric coleons ((15S)-coleon C ((15 S)-1a), and (15S)-coleon D ((15S)-2a)) in Plectranthus lanuginosus [1], The proposed structures have now been proven by careful comparison of their physical data with those of the already described C(15)-epimers whose structures were deduced by X-ray analysis of a derived cis-diketone 3 [5], Examination of the epimeric purity of coleons possessing a 2-hydroxy-1-methylethyl side-chain (coleons C, D, H, I, I′ and derivatives) isolated from seven different species (Coleus, Plectranthus and Solenostemon) has shown that these coleons always occur as a mixture of C(15)-epimers, although in most cases with one predominant epimer. The consequences for the stereochemistry of the postulated in vivo formation of the methyl-substituted spirocyclopropane substructure is discussed.

Notes: Spirocoleons: Synthesis and Characterization of Four Diastereomeric Spiro (methylcyclopropane) Substructures; Revision of the Configuration at C(12) and C(15) of Coleon P and Derivatives and Coleon-Z Derivatives; X-Ray Analysis of Lanugon J and of Further SpirocoleonsX-ray analyses show the correctness of the previously published structure of coleon Q (1), establish the structure of lanugon J (4a), and necessitate a revision of the configuration at C(12) and C(15) in coleon P (3a) and its derivatives 3b and 3c, and furthermore of the coleon Z derivatives 11a-11d. Two further diastereomeric spiro (methylcyclopropane) substructures have been generated by photoisomerization of lanugon J (4a) and 12-O-desacetylcoleon N (8); they represent the novel cis-type B with (12R, 13R, 15S)- and the novel trans-type D with (12R, 13R, 15R)-configuration (Scheme 1). The structures of the photoproducts 5a ((12R, 13R, 15R)-lanugon J) and 7a ((12R, 13R, 15S)-lanugon J) were established by X-ray analysis. So far, only two of the eight possible diastereomers of the spiro-(methylcyclopropane) substructure I have been detected in nature, i.e. the trans-type A with (12R, 13S, 15S)- and the cis-type C with (12R, 13S, 15R)-configuration. The four diastereomers A-D, all possessing (12R)-configuration, show very similar properties. However, careful comparison of spectral and chiroptical data allow a differentiation, even in the case of functionalization of H3C(17). The (12S)-counter-parts could not yet be prepared.

Notes: Pigments from Leaf-Glands from Labiatae: 17 Quinonoid Abietanoids from Plectranthus sanguineus BRITTENFrom the glandular trichomes of the title plant from Nyasaland, Malawi, 17 abietanoid quinones and hydroquinones were isolated and identified, the most interesting amongst them being the novel tricyclic, sevenmembered anhydride 8. A detailed HPLC separation of the compounds is presented.

Notes: Structure of Edulon ABased on new chemical reactions and an X-ray analysis of the derived camphanic ester 2e, edulon A has been shown to have the structure 2a, i.e. (10bS, 1′S)-8-(2′-acetoxy-1′-methylethyl)-2,4,6, 10b-tetrahydro-7,9, 10-trihydroxy-3, 10b-dimethyl-1H-5-oxaaceanthrylene-4,6-dione. Therefore, it is not a 2H-1-oxapyrene as previously assumed, but a derivative of the novel 4H-5-oxaaceanthrylene skeleton.