Control of the diels-alder addition regioselectivity by remote substituents. Synthesis of anthracycline precursors.

Lee

et al. 2013

IJMS

Two new norsesquiterpenoids, solanerianones A and B (1–2), together with nine known compounds, including four sesquiterpenoids, (−)-solavetivone (3), (+)-anhydro-β-rotunol (4), solafuranone (5), lycifuranone A (6); one alkaloid, N-trans-feruloyltyramine (7); one fatty acid, palmitic acid (8); one phenylalkanoid, acetovanillone (9), and two steroids, β-sitosterol (10) and stigmasterol (11) were isolated from the n-hexane-soluble part of the roots of Solanum erianthum. Their structures were elucidated on the basis of physical and spectroscopic data analyses. The anti-inflammatory activity of these isolates was monitored by nitric oxide (NO) production in lipopolysaccharide (LPS)-activated murine macrophage RAW264.7 cells. The cytotoxicity towards human lung squamous carcinoma (CH27), human hepatocellular carcinoma (Hep 3B), human oral squamous carcinoma (HSC-3) and human melanoma (M21) cell lines was also screened by using an MTT assay. Of the compounds tested, 3 exhibited the strongest NO inhibition with the average maximum inhibition (Emax) at 100 μM and median inhibitory concentration (IC50) values of 98.23% ± 0.08% and 65.54 ± 0.18 μM, respectively. None of compounds (1–9) was found to possess cytotoxic activity against human cancer cell lines at concentrations up to 30 μM.

Section: Discussionmentioning

confidence: 99%

Anti-Inflammatory Components from the Root of Solanum erianthum

Lee

et al. 2013

IJMS

“…1100. 'H-NMR(CDCI3): 5.15 (t, 3J = 5.3, H-C(4)); 4.73 (s, CH-C(1));3.72 (dd, 'J = 6.7,5.3, H-C(3), H-C(5)); 3.71, 3.64(23,4 COOCH,); 3.35 (s, (CH,O),CH); 3.24 (d, ' J = 6.7, H-C(2), H-C(6)). "C-NMR (CDCI,): 171.6, 169.6 (2m, 4 C); 101.5 (dm, 'J(C,H) = 161, CH-C(1)); 95.6 (m, C(1)); 78.3 (dm, 'J(C,H) = 161, C(4)); 55.5 (qd, 'J(C,H) = 143, 'J(C,H) = 5, (CH,O),CH); 52.0, 51.5 (2q, 'J(C,H) = 147, COOCH,); 49.9, 48.2 (2d, 'J(C,H) = 132,C(2),C(3),C(5),C(6)).…”

mentioning

confidence: 99%

Diels‐AlderRegioselectivity Controlled by Remote Substituents. The Cycloadditions of 1‐(Dimethoxymethyl)‐2,3‐dimethylidene‐ and ‐2,3,5,6‐tetramethylidene‐7‐oxabicyclo[2.2.1]heptanes

Métral

Lauterwein

Vogel

1986

Helvetica Chimica Acta

Self Cite

The syntheses of 2,3-dimethylidene-and 2,3,5,6-tetramethylidene-7-oxabicyclo[2.2. llheptanes substituted in position C(1) are reported. The 1-dimethoxymethyl group in derivatives 2 and 6 controls the regioselectivity of the Lewis-acid-catalyzed Diels-Alder additions with methyl vinyl kctone and butynone. For the EtAIC1,-catalyzed addition of methyl vinyl ketone to 6, the regioselectivity can be reversed by a small solvent modification. The tetraene 2 is a versatile reagent for regioselective 'tandem' cycloadditions.

“…No inter-ring 'J(H,H) (< 0.2 Hz) could be detected for Hendo-C(3) and Hendo-C(6), whereas at 5J(H,H) = 0.8 Hz in 7 and 1.1-1. 4 Hz in 8-12 was measured for Hexo-C (3) and Hexo-C(6). CNDOj2 and INDO calculations on model molecules (see below, Table 3 and Fig.…”

mentioning

confidence: 99%

¹H‐NMR Spectra of Cyclohexa‐1,4‐dienes and Cyclohexenes Annellated to Bicyclo[2.2.1]hept‐2‐enes. The Inter‐Ring Homoallylic H,H Coupling Constants as Stereochemical Probes

Mahaim

Carrupt

Vogel

1985

Helvetica Chimica Acta

Self Cite

l]hept-2-enebond n-anisotropy. Vicinal as well as intra-ring homoallylic coupling constants are consistent with a small puckering of the cyclohexa-I ,4-diene rings toward the rndo -face. The allylic exo-methylene protons are more deshielded than the cvzdo-protons independent of the nature of the suhstituents, the nature of the bridges, and the degree of unsaturation of the annellated systems. These results constitute a probe for the configuration of cyclohexa-l,4-dienes and cyclohexenes annellated to these bicyclic skeletons.Introduction. -In the course of our studies on the synthesis of anthracyclines [I-41 based on the Diels-Alder additions of exocyclic s-cis-butadiene moieties grafted onto 7-oxabicyclo[2.2. Ilheptane derivatives 1, we observed 'H-NMR spectra of the corresponding adducts 2 with measurable homoallylic 'J(H,H) coupling constants of ca. 1 Hz between the bridgehead protons of the 7-oxabicyclo[2.2. llheptene systems and the allylic protons of the annellated cyclohexene moieties [3-51. This was true for the exo-protons only; no such long-range coupling could be detected for the endo-allylic protons. In order to determine whether this feature could be taken as a probe for the configuration of the Diels-Alder adducts 2, we prepared a series of cyclohexenes and cyclohexa-1,Cdienes annellated to various bicyclo[2.2.l]hept-2-ene and 7-oxabicyclo[2.2.l]hept-2-ene skeletons. We report now on their high-field (360 MHz) 'H-NMR properties and show that the inter-ring homoallylic 'J(H,H) coupling constants indeed constitute the probe we were looking for.