Synthesis and Structure of Novel Haloselenurane−Lewis Acid Complexes

Saito, Shinichi; Zhang, Jian; Koizumi, Toru

doi:10.1021/jo980215f

Cited by 7 publications

(1 citation statement)

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“…576 The structure of 467 (R = Ph) has been verified by X-ray analysis, and the allylated derivatives 467 (R = CH 2 CH᎐ ᎐ CR 1 R 2 ) undergo [2,3]-sigmatropic rearrangement to give products 468 which have been transformed into allylic alcohols 469 of 32-88% ee. The chlorooxaphenylselenurane 466 (X = Cl; R = Ph) reacts 577 with HgCl 2 to give the Lewis acid complex 470 or with AgBF 4 to give 471 whose structures were determined by X-ray methods. The compound 471 has been shown to be a fluoroselenurane-BF 3 complex on the basis of an observed covalent interaction between Se and one F atom.…”

Section: Camphanes and Isocamphanesmentioning

confidence: 99%

Monoterpenoids (mid-1997 to mid-1999)

Grayson

2000

Nat. Prod. Rep.

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In situ RNA hybridization and immunocytochemistry were used to establish the cellular distribution of monoterpenoid indole alkaloid biosynthesis in Madagascar periwinkle (Catharanthus roseus). Tryptophan decarboxylase (TDC) and strictosidine synthase (STR1), which are involved in the biosynthesis of the central intermediate strictosidine, and desacetoxyvindoline 4-hydroxylase (D4H) and deacetylvindoline 4-O-acetyltransferase (DAT), which are involved in the terminal steps of vindoline biosynthesis, were localized. tdc and str1 mRNAs were present in the epidermis of stems, leaves, and flower buds, whereas they appeared in most protoderm and cortical cells around the apical meristem of root tips. In marked contrast, d4h and dat mRNAs were associated with the laticifer and idioblast cells of leaves, stems, and flower buds. Immunocytochemical localization for TDC, D4H, and DAT proteins confirmed the differential localiza-tion of early and late stages of vindoline biosynthesis. Therefore, we concluded that the elaboration of the major leaf al-kaloids involves the participation of at least two cell types and requires the intercellular translocation of a pathway intermediate. A basipetal gradient of expression in maturing leaves also was shown for all four genes by in situ RNA hy-bridization studies and by complementary studies with dissected leaves, suggesting that expression of the vindoline pathway occurs transiently during early leaf development. These results partially explain why attempts to produce vin-doline by cell culture technology have failed. INTRODUCTION The organs forming the plant body consist of several different cell types that are organized in relation to each other and that confer specific functions to the resulting organ. Each cell type emerges from an undifferentiated meristem according to a sophisticated and partially understood developmental program (Sylvester et al., 1996; von Arnim and Deng, 1996). The commitment to differentiate into specialized structures involves the perception by cells in the meristem of a complex array of signals, which communicate cellular age, position in relation to other cells, and hormonal balance. Environmental factors, such as light and temperature, also play a critical role in modulating these signals throughout the process of organogenesis (Bernier, 1988; Dale, 1988; Sylvester et al., 1996). In addition to morphogenesis, developmental processes result in biochemical specialization of cells for the biosyn-thesis and/or accumulation of secondary metabolites, such as phenylpropanoids (Ibrahim et al.

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Section: Camphanes and Isocamphanesmentioning

confidence: 99%

Monoterpenoids (mid-1997 to mid-1999)

Grayson

2000

Nat. Prod. Rep.

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NMR of Organoselenium and Organotellurium Compounds

Panda

Singh

2012

Patai's Chemistry of Functional Groups

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This chapter gives a systematic account of and surveys the available data on 77 Se and 125 Te NMR spectra of organochalcogen compounds such as chacogenols, mono and dichalcogenides, chalcogenolates, tetra and hexa substituted chalcogen compounds, chalcogenyl halides, chalcogen‐containing heterocycles and macrocycles, chalcogen‐oxygen/nitrogen compounds, etc. The review is based on the literature from 1985 to 2011 and includes 780 references. The 77 Se/ 125 Te NMR spectra of organochalcogen compounds reveal expansive chemical shifts (δ Se /δ Te ) leading to sharp sensitivity of these nuclei (Se/Te) to their environment such as solvent, temperature, molecular geometry, ligand backbone, oxidation state, chelate ring size, steric strain, etc. This is well illustrated by the advantageous use of this spectroscopy in the successful determination of the solution state structure of several organochalcogen compounds. It is noted that the 125 Te and 77 Se chemical shifts of a large number of structurally similar organotellurium and selenium compounds show linear relationship.

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