Two new bromoindoles from red alga Laurencia similis

Two new bromoindole alkaloids have been isolated from the ethanolic extract of the red alga Laurencia similis. On the basis of chemical and spectroscopic methods (including 1D and 2D NMR technique), their structures have been elucidated as 2,2',5,5',6,6'-sixibromo-3, 3'-bi-1H-indole and 3, 5-dibromo-1-methylindole, respectively. (C) 2008 Xiao Bin Zhu. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

A new halogenated biindole and a new apo-carotenone from green alga Chaetomorpha basiretorsa Setchell

A new halogenated biindole and a new apo-carotenone have been isolated from the ethanolic extract of the green alga Chaetomorpha basiretorsa Sethcell. On the basis of chemical and spectroscopic methods including 2D NMR technique, their structures have been elucidated as 4,4'-dichloro-5,5'-dibromo-7,7'-dimethoxy-2,2'-bi-1H-indole and 1'S*,4R*-8-(4'-hydroxy-2',6',6'-trimethylcyclohex-2-enyl)-6-methyloct-3E,5E,7E-trien-2-one, respectively.

A novel polyhydroxyl sterol from Asterina pectinifera

A novel polyhydroxyl sterol ( 1) along with one known polyhydroxyl sterol (2), and two known monoglycosides, asterosaponin P-1 (3) and its desulfated monoglycoside (4), have been isolated from the whole bodies of a common Pacific starfish Asterina pectinifera. The structure of the new polyhydroxyl sterol was determined as 15beta, 16beta-isopropylidenedioxy-5alpha-cholestane-3beta, 4beta, 6alpha, 7alpha, 8,26-hexaol by spectroscopic methods, including FABMS, HR-FABMS, 1D and 2D NMR techniques.

A new sesquiterpene-substituted benzoic acid from the brown alga Dictyopteris divaricata.

A new sesquiterpene-substituted benzoic acid has been isolated from the brown Alga Dictyopteris divaricata Okam.. Its structure was elucidated as 3-[(2-hydroxy-2,5,5,8a-tetramethyldecahydro-1-naphthalenyl)methyl]-4-hydroxybenzoic acid, named dictyvaric acid on the basis of spectroscopic methods including IR, HRFABMS, 1D and 2D NMR techniques.

A new bromophenol from the brown alga Leathesia nana

A novel bromophenol was isolated from ethanolic extract of the brown alga Leathesia nana S.et G. The structure was elucidated as (E)-3-(2,3-dibromo-4,5-dihydroxyphenyl)-2-methyl-propenal by spectroscopic methods including IR, HREIMS, ID and 2D NMR techniques.

Two new bromophenols from red alga Rhodomela confervoides

Two new bromophenols were isolated from Rhodomela confervoides. Their structures were elucidated as 2, 2', 3-tribromo-3', 4, 4', 5-tetrahydroxy-6'-hydroxymethyldiphenylmethane and 2, 2', 3-tribromo-3', 4, 4', 5-tetrahydroxy-6'-ethyloxymethyldiphenylmethane by spectroscopic methods including IR, HREIMS, 1D and 2D NMR techniques.

A new poly brominated dibenzylphenol from Rhodomela confervoides

A new poly brominated dibenzylphenol named as rhodomevoidin was isolated from Rhodomela confervoides. Its structrue was elucidated as 3-bromo-4, 5-bis (2, 3-dibromo-4, 5-dihydroxybenzyI)pyrocatechol by spectroscopic methods including IR, HRFABMS, 1D and 2D NMR techniques.

Two new norisoprenoid derivatives from the red alga Gymnogongrus flabelliformis

Two new norisoprenoid derivatives have been isolated from the red alga Gymnogongrus flabelliformis. Their structures were elucidated as (3R, 6R, 7E)-(+)-3-O-phenylacetyl-4,7-megastigmadiene-9-one and (3R,7E)-(-)-3-O-phenylacetyl-5,7-megastigmadiene-9-one, respectively, by spectroscopic methods including HRMS, 1D and 2D NMR techniques.

The glycosides from Lomatogonium rotatum

A new phenyl glycoside, 2-(3'-O-beta-D-glucopyranosyl) benzoyloxygentisic acid (1), along with seven known glycosides 2-8 was isolated from Tibetan herbal medicine Lomatogonium rotatum. The structures of the compounds were elucidated by spectroscopic methods including 1D and 2D NMR techniques and MS data.

Skeleton-rearranged pentacyclic diterpenoids possessing a cyclobutane ring from Euphorbia wallichii

Two novel rearranged trachylobane diterpenoids, designated as wallichanol A (2) and wallichanol B (3), consisting of an unprecedented pentacyclic skeleton named wallichane with a cyclobutane ring, and a new ent-trachylobane diterpenoid, 3-oxo-ent-trachyloban-17-oic acid (1), were isolated from the roots of Euphorbia wallichii. Their structures were elucidated by comprehensive analysis of 2D-NMR spectroscopic data, with the stereochemistry of 1 confirmed by X-ray crystallographic study. All of these compounds potently block osteoclastogenesis in vitro, suggesting a potential therapeutic application in prevention of osteoporosis.

A new daphnane diterpene from Daphne tangutica

A new daphnane diterpene was isolated from the root barks of Daphne tangutica Maxim. Its structure was elucidated as 1, 2 alpha-dihydro-20-palimoyldaphnetoxin by the spectroscopic evidence including 2D-NMR.

Synteza i struktura nowych aminowych analogów ansamycynowego antybiotyku rifampicyny

Wydział Chemii: Zakład Biochemii

Synthesis and reactivity of pyridine substituted α-diazocarbonyl compounds and exploration of rhodium carboxylates as asymmetric catalysts

The primary objective of this thesis was the preparation of a series of pyridine-containing α-diazocarbonyl compounds and subsequent investigation of the reactivity of these compounds on exposure to transition metal catalysts. In particular, the reactivity of the pyridyl α-diazocarbonyls was compared to that of the analogous phenyl α-diazocarbonyl compounds to ascertain the impact of replacement of the phenyl ring with pyridine. The first chapter initially provides a brief introduction into α-diazocarbonyl chemistry, comprising a compendium of well-established and recently developed methods in the preparation of these compounds, as well as an outline of the reactivity of these versatile substrates. The substantive element of this introductory chapter comprises a detailed review focused on transition metal-catalysed transformations of heterocyclic α-diazocarbonyl compounds, highlighting the extraordinary diversity of reaction products which can be accessed. This review is undertaken to set the work of this thesis in context. The results of this research are discussed in the second and third chapters together with the associated experimental details, including spectroscopic and analytical data obtained in the synthesis of all compounds during this research. The second chapter describes the preparation of a range of novel pyridine-containing α-diazocarbonyl compounds via a number of synthetic strategies including both acylation and diazo transfer methodologies. In contrast to the phenyl analogues, the generation of the pyridine α-diazocarbonyl substrates was complicated by a number of factors including the inherent basicity of the pyridine ring, tautomerism and existence of rotamers. Rhodium- and copper-mediated transformations of the pyridine-containing α-diazocarbonyl compounds is discussed in detail displaying very different reactivity patterns to those seen with the phenyl analogues; oxidation to 2,3- diketones, 1,2-hydride shift to form enones and oxonium and sulfonium ylide formation/rearrangement are prominent in the pyridyl series, with no evidence of aromatic addition to the pyridine ring. The third chapter focuses on exploration of novel chiral rhodium(II) catalysts, developed in the Maguire team, in both intermolecular cyclopropanations and intramolecular C–H insertion reactions. In this chapter, the studies are focused on standard α-diazocarbonyl compounds without heteroaryl substituents. The most notable outcome was the achievement of high enantiopurities for intramolecular C–H insertions, which were competitive with, and even surpassed, established catalyst systems in some cases. This work has provided insight into solvent and temperature effects on yields as well as enantio- and diastereoselectivity, thereby providing guidance for future development and design of chiral rhodium carboxylate catalysts. While this is a preliminary study, the significance of the results lie in the fact that these are the first reactions to give substantial asymmetric induction with these novel rhodium carboxylates. While the majority of the α-diazocarbonyl compounds explored in this work were α-diazoketones, a number of α-diazoesters are also described. Details of chiral stationary phase HPLC analysis, single crystal analysis and 2D NMR experiments are included in the Appendix (Appendix III-V).

PATENSIN, A SAPONIN FROM PULSATILLA PATENS VAR MULTIFIDA

Patensin, a new triterpenoid glycoside, was isolated from the ethanolic extraction of the roots of Pulsatilla patens var. multifida. Its structure was established as hederagenin 3-O-beta-D-galactopyranosyl-(1-->2)-beta-D-glucopyranoside on the basis of hydrolysis and spectral evidence including 1D and 2D NMR techniques.

Síntese de derivados oligoméricos de porfirinas e ftalocianinas

A presente dissertação contempla estudos de funcionalização de 5,10,15,20- tetrafenilporfirina via grupos nitro e amino e a preparação de sistemas porfirina-ftalocianina. Este trabalho encontra-se dividido em quatro partes. Na primeira parte descrevem-se as características gerais de porfirinas e ftalocianinas bem como algumas metodologias de síntese utilizadas na sua preparação e suas potenciais aplicações. Na segunda parte desta dissertação descreve-se a funcionalização de 5,10,15,20-tetrafenilporfirina com arilaminas recorrendo a duas rotas sintéticas diferentes. A reacção de 2-nitro-5,10,15,20-tetrafenilporfirina com anilina ou aminas aromáticas substituídas com grupos dadores de electrões permitiu, através do ataque do nucleófilo ao carbono beta-pirrólico onde está ligado o grupo nitro, ataque ipso, a obtenção de derivados do tipo 2-arilaminoporfirinas e derivados porfirínicos de anéis fundidos, sendo estes últimos resultantes da ciclização oxidativa de 2-arilaminoporfirinas. A reacção entre (2-amino- 5,10,15,20-tetrafenilporfirinato)níquel(II) e brometos de arilo na presença de paládio, reacção de aminação de Buchwald-Hartwig, permitiu, após descomplexação, a preparação de novos derivados do tipo 2- arilaminoporfirinas com grupos substituintes dadores e aceitadores de electrões. Um dos derivados porfirínicos de anéis fundidos foi submetido a reacção de complexação com diferentes iões metálicos e foram estudadas as respectivas propriedades fotoquímicas e electroquímicas. Esses estudos revelaram que estes compostos são bons geradores de oxigénio singuleto e que sofrem processos de oxidação-redução electroquimicamente reversíveis. Esta metodologia foi estendida ainda a brometos de hetarilo (derivados de piridina e tiofeno). Recorrendo ao acoplamento, em condições de Buchwald-Hartwig, de complexos metálicos da 5,10,15,20-tetrafenilporfirina, funcionalizados com grupos amino e bromo, preparam-se dímeros porfirina-amino-porfirina, cujos espectros electrónicos revelam a existência de uma boa “comunicação electrónica” entre as duas subunidades. A terceira parte descreve a síntese de sistemas porfirina-ftalocianina. Recorrendo à condensação estatística entre a 5,10,15,20-tetrafenilporfirina substituída com um grupo ftalonitrilo na posição beta-pirrólica com ftalonitrilo ou ftalonitrilo substituído foram obtidas díades porfirina-ftalocianina onde as duas subunidades se encontram directamente ligadas ou fundidas. Os porfirinilftalonitrilos necessários para a síntese das diferentes díades foram preparados através da reacção de adição do fumaronitrilo à 5,10,15,20- tetrafenilporfirina funcionalizada com o grupo 1,3-butadienilo ou vinilo, seguida de oxidação do aducto resultante. O acoplamento catalisado por paládio entre (2-bromo-5,10,15,20- tetrafenilporfirinato)zinco(II) e [9(10),16(17),23(24)-tri-terc-butil-2- etinilftalocianinato]zinco(II) permitiu a síntese de uma díade porfirinaftalocianina com as duas unidades ligadas por um grupo etinilo. Uma pentíade porfirina-ftalocianina foi obtida através da ciclotetramerização de um dos porfirinilftalonitrilos. A comparação dos espectros electrónicos das diferentes classes de sistemas revela que as correspondentes propriedades electrónicas são altamente afectadas pela distância entre as subunidades e também pelo número de cromóforos presentes no sistema. Os estudos fotofísicos de alguns dos novos compostos acima referidos permitiram verificar a ocorrência eficiente de transferência de energia da subunidade porfirínica para a da ftalocianina, capacidade essa que permitirá a estes sistemas serem usados para modelar o processo fotossintético. Na última parte descrevem-se, pormenorizadamente, todas as experiências efectuadas e as caracterizações espectroscópicas, nomeadamente de espectroscopia de ressonância magnética nuclear (RMN), espectrometria de massa e espectrofotometria de UV-vis, dos compostos sintetizados. Nalguns casos recorreu-se ainda a técnicas de RMN bidimensionais como COSY, HSQC, HMBC, NOESY e ROESY.