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Molecules, Volume 7, Issue 1 (January 2002), Pages 1-103

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Research

Open AccessArticle Natural Products from Three Nudibranchs: Nembrotha kubaryana, Hypselodoris infucata and Chromodoris petechialis
Molecules 2002, 7(1), 1-6; doi:10.3390/70100001-rev
Received: 26 October 2001 / Revised: 10 November 2001 / Accepted: 12 November 2001 / Published: 31 January 2002
Cited by 6 | PDF Full-text (30 KB) | HTML Full-text | XML Full-text | Correction
Abstract
Nudibranchs are shell-less molluscs that are often brightly colored and seemingly defenseless against predation. However, these beautiful animals usually contain large amounts of diet-derived natural products that help defend them against predation. We have isolated a blue tetrapyrrole from Nembrotha kubaryana, the
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Nudibranchs are shell-less molluscs that are often brightly colored and seemingly defenseless against predation. However, these beautiful animals usually contain large amounts of diet-derived natural products that help defend them against predation. We have isolated a blue tetrapyrrole from Nembrotha kubaryana, the known nakafuran-8 and -9 from Hypselodoris infucata and spongiane-16-one from Chromodoris petechialis. These compounds have previously been found in other marine organisms, thus supporting a link between diet and natural products in the nudibranchs. Full article
Open AccessArticle Preparation of Substituted Methyl o-Nitrophenyl Sulfides
Molecules 2002, 7(1), 7-17; doi:10.3390/70100007
Received: 27 September 2001 / Revised: 9 November 2001 / Accepted: 13 November 2001 / Published: 31 January 2002
Cited by 5 | PDF Full-text (101 KB) | HTML Full-text | XML Full-text
Abstract
The nucleophilic substitution of substituted o-nitrochlorobenzenes with substituted methanethiolates, catalysed with triethylamine or pyridine, has been used to prepare a series of appropriately substituted methyl-o-nitrophenylsulfides. The prepared compounds were identified by their 1H- and 13C-NMR spectra. The base catalysed ring closure
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The nucleophilic substitution of substituted o-nitrochlorobenzenes with substituted methanethiolates, catalysed with triethylamine or pyridine, has been used to prepare a series of appropriately substituted methyl-o-nitrophenylsulfides. The prepared compounds were identified by their 1H- and 13C-NMR spectra. The base catalysed ring closure of methyl 2-(methoxycarbonylmethylsulfanyl)-3,5-dinitrobenzenecarboxylate only results in an attack of carbanion on the ester group, not on a nitro group as with the other compounds prepared. The cyclisation product is methyl 3-hydroxy-5,7-dinitrobenzo[b]thiophene-2-carboxylate (11). Full article
Open AccessArticle Synthesis of Precursors for the Oxidative Tandem Cyclization of Diphenols to Galanthamine Analogs
Molecules 2002, 7(1), 18-25; doi:10.3390/70100018
Received: 1 November 2001 / Revised: 19 November 2001 / Accepted: 20 November 2001 / Published: 31 January 2002
Cited by 4 | PDF Full-text (39 KB) | HTML Full-text | XML Full-text
Abstract Methods for the preparation of 4-bromo-5-[2-(4-hydroxybenzyl)benzyl]-2-methoxyphenol and 4-bromo-5-[4-(4-hydroxyphenyl)butyl]-2-methoxyphenol are described. Full article
Open AccessArticle Fractal Hybrid Orbitals Analysis of the Tertiary Structure of Protein Molecules
Molecules 2002, 7(1), 26-37; doi:10.3390/70100026
Received: 9 November 2001 / Revised: 28 November 2001 / Accepted: 28 November 2001 / Published: 31 January 2002
Cited by 6 | PDF Full-text (90 KB) | HTML Full-text | XML Full-text
Abstract
The structure and shape of the polypeptide chains of proteins are determined by the hybridized states of the atomic orbitals in the molecular chain. The calculated s ratio in the spn hybrid orbitals is computed from the fractal dimension D of the
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The structure and shape of the polypeptide chains of proteins are determined by the hybridized states of the atomic orbitals in the molecular chain. The calculated s ratio in the spn hybrid orbitals is computed from the fractal dimension D of the tertiary structures of 43 proteins selected to cover the five structural classes of protein molecules. A brief introduction to fractal theory is given in the text. It is demonstrated that the principles dictating the folding of the local and global backbone structures are well characterized in terms of the representation given by fractal theory. Comparison of the fractal character of protein molecules with that of the ideal Gaussian chain revealed several features of these principles. It is also shown that proteins in the β type structural class are distinguished quantitatively from those in other classes with this representation. They show a higher s ratio (0.32) in sp2.20 hybrids, rather similar to planar sp2. Comparison of the proteins with a Gaussian chain is interpreted in terms of steric repulsion. Full article
Open AccessArticle Thirteen New Xanthone Derivatives from Calophyllum caledonicum (Clusiaceae)
Molecules 2002, 7(1), 38-50; doi:10.3390/70100038
Received: 11 October 2001 / Revised: 28 November 2001 / Accepted: 28 November 2001 / Published: 31 January 2002
Cited by 10 | PDF Full-text (63 KB) | HTML Full-text | XML Full-text
Abstract
An EtOAc extract of the stem bark of Calophyllum caledonicum (Clusiaceae) yielded thirteen new hydroxylated and/or prenylated xanthone derivatives, namely 5-hydroxy-8-methoxyxanthone (1), 3,5-dihydroxy-1,2-dimethoxyxanthone (2), 1,8-dihydroxy-6,7-dimethoxyxanthone (3), 5,7-dihydroxy-2,6-dimethoxyxanthone (4), 6,8-dihydroxy-3,7-dimethoxy-xanthone (5), 2,5,6,7,8-pentahydroxyxanthone (6), 1,3,8-trihydroxy-5,7-dimethoxyxanthone (7) and according to a previously adopted nomenclature [3], caledonixanthone
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An EtOAc extract of the stem bark of Calophyllum caledonicum (Clusiaceae) yielded thirteen new hydroxylated and/or prenylated xanthone derivatives, namely 5-hydroxy-8-methoxyxanthone (1), 3,5-dihydroxy-1,2-dimethoxyxanthone (2), 1,8-dihydroxy-6,7-dimethoxyxanthone (3), 5,7-dihydroxy-2,6-dimethoxyxanthone (4), 6,8-dihydroxy-3,7-dimethoxy-xanthone (5), 2,5,6,7,8-pentahydroxyxanthone (6), 1,3,8-trihydroxy-5,7-dimethoxyxanthone (7) and according to a previously adopted nomenclature [3], caledonixanthone G-L. (8-13). The structural elucidation of 1-13 were mainly established on the basis of 1D and 2D NMR and HRMS spectroscopic analysis. Full article
Open AccessArticle Virtual Screening in Lead Discovery: A Viewpoint
Molecules 2002, 7(1), 51-62; doi:10.3390/70100051
Received: 22 October 2001 / Revised: 9 December 2001 / Accepted: 12 December 2001 / Published: 31 January 2002
Cited by 39 | PDF Full-text (51 KB) | HTML Full-text | XML Full-text
Abstract
Virtual screening (VS) methods have emerged as an adaptive response to massive throughput synthesis and screening technologies. Based on the structure-permeability paradigm, the Lipinski rule of five has become a standard property filtering protocol for VS. Three possible VS scenarios with respect to
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Virtual screening (VS) methods have emerged as an adaptive response to massive throughput synthesis and screening technologies. Based on the structure-permeability paradigm, the Lipinski rule of five has become a standard property filtering protocol for VS. Three possible VS scenarios with respect to optimising binding affinity and pharmacokinetic properties are discussed. The parsimony principle for selecting candidate leads for further optimisation is advocated. Full article
Open AccessArticle ElectronTransfer Induced Ring Opening of α-Epoxyketones: Spirodioxolane Formation
Molecules 2002, 7(1), 63-71; doi:10.3390/70100063
Received: 21 June 2001 / Revised: 17 November 2001 / Accepted: 13 December 2001 / Published: 31 January 2002
Cited by 2 | PDF Full-text (131 KB) | HTML Full-text | XML Full-text
Abstract Stereospecific formation of spirodioxolanes has been observed on electron transfer induced ring opening of α-epoxyketones by 2,4,6-triphenylpyrylium tetrafluoroborate in the presence of cyclohexanone Full article
Open AccessArticle Lithium Perchlorate Mediated Three-Component Preparation of Primary Aminoesters
Molecules 2002, 7(1), 72-74; doi:10.3390/70100072
Received: 18 September 2001 / Revised: 6 December 2001 / Accepted: 14 December 2001 / Published: 31 January 2002
Cited by 1 | PDF Full-text (23 KB) | HTML Full-text | XML Full-text
Abstract A three-component reaction between an aldehyde, metallated hexamethyldisilazane and a functionalized organozinc compound proceeded smoothly in the presence of LiClO4 in diethyl ether to afford primary amino esters in good yields. Full article
Open AccessArticle New Phenylpropanoid Glucosides from Eucalyptus maculata
Molecules 2002, 7(1), 75-80; doi:10.3390/70100075
Received: 25 October 2001 / Revised: 23 December 2001 / Accepted: 24 December 2001 / Published: 30 January 2002
Cited by 7 | PDF Full-text (33 KB) | HTML Full-text | XML Full-text
Abstract Three compounds were isolated from the butanol soluble fraction of the resinous exudate from the stem of Eucalyptus maculata. In addition to p-coumaric acid two new compounds were identified. They were identified as 1-O-cinnamoyl 6-O-pcoumaroylglucose and 7-methyl-aromadendrin-4′-O-(6′′-trans-p-coumaroyl)-β-D-glucopyranoside by spectroscopic and chemical means. Full article
Open AccessArticle The Behaviour of 1,2,3-Indantrione Towards Wittig-Horner Reagents
Molecules 2002, 7(1), 81-88; doi:10.3390/70100081
Received: 1 October 2000 / Revised: 6 August 2001 / Accepted: 10 August 2001 / Published: 30 January 2002
Cited by 1 | PDF Full-text (47 KB) | HTML Full-text | XML Full-text
Abstract
Wittig-Horner reagents 1a,b react with 1,2,3-indantrione (2) to give the dimeric adducts 3a and 3b, respectively. Moreover, 2 reacts with tert-butyl diethylphosphonoacetate (1c) yielding the ethylenic compound 4. On the other hand, 2 reacts with 1d to yield the phosphonate adduct 5. Mechanisms
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Wittig-Horner reagents 1a,b react with 1,2,3-indantrione (2) to give the dimeric adducts 3a and 3b, respectively. Moreover, 2 reacts with tert-butyl diethylphosphonoacetate (1c) yielding the ethylenic compound 4. On the other hand, 2 reacts with 1d to yield the phosphonate adduct 5. Mechanisms accounting for the formation of the new products are discussed and the probable structures of the products are presented based on compatible analytical and spectral data. Full article
Open AccessArticle Three-Component Halo Aldol Condensation of Thioacrylates with Aldehydes Mediated by Titanium (IV) Halide
Molecules 2002, 7(1), 89-95; doi:10.3390/70100089
Received: 28 June 2001 / Revised: 19 December 2001 / Accepted: 21 December 2001 / Published: 30 January 2002
Cited by 3 | PDF Full-text (32 KB) | HTML Full-text | XML Full-text
Abstract
a,b-Ethyl thioacrylate was difuctionalized by a tandem X-C/C=C bond formation reaction. The new system uses Ti (IV) halide as both the Lewis acidic promoter and the halogen source for the Michael-type addition onto the thioacrylate. The titanium enolate species resulting from Michael-type addition
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a,b-Ethyl thioacrylate was difuctionalized by a tandem X-C/C=C bond formation reaction. The new system uses Ti (IV) halide as both the Lewis acidic promoter and the halogen source for the Michael-type addition onto the thioacrylate. The titanium enolate species resulting from Michael-type addition react with aldehydes followed by dehydration to afford trisubstituted olefin products. Complete geometric selectivity (>95%) and up to 72% yield have been obtained for 7 examples. Full article
Open AccessArticle Synthesis of Heterocyclic Skeletons by the Reaction of N1-(2-Cyanophenyl)-benzimidoyl Chloride with Thioamides
Molecules 2002, 7(1), 96-103; doi:10.3390/70100096
Received: 27 December 2001 / Revised: 24 January 2002 / Accepted: 24 January 2002 / Published: 30 January 2002
Cited by 10 | PDF Full-text (91 KB) | HTML Full-text | XML Full-text
Abstract The reaction of N-(2-cyanophenyl)benzimidoyl chloride with reagents containing a thioamide moiety, i.e. thioacetamide, benzylthiourea, symmetrical dialkyl- and diarylthioureas gave different cyclic products: 3,1-benzothiazine, 1,3,5-benzotriazocine and quinazoline. The reaction pathways of prepared compounds are discussed. Full article

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