1,720,962 research outputs found
MOLISE: L’ANTICA RETE DEI TRATTURI E L’INSEDIAMENTO ANTROPICO ATTUALE. Le trasformazioni del sistema insediativo dalla fine della transumanza alle recenti realizzazioni infrastrutturali
No full textDa lungo tempo l'immagine prevalente del Molise è quella di uno spazio geografico compatto con caratteri omogenei. Questa immagine, utilizzata come riferimento per politiche territoriali e di realizzazione di grandi opere, oggi non appare più adatta di fronte alla varietà e alla complessità che vanno assumendo le forme del territorio regionale.
Qesta pubblicazione, prodotta nell'ambito della ricerca ITATeN, intende mettere in evidenza alcune differenze emergenti, identificando aree caratterizzate da specifici processi economico-produttivi e da specifiche morfologie insediative.
L'attenzione si rivolge in particolare, agli insediamenti insediativi locali dove i segni del paesaggio storico e naturale combinati con quelli della contemporaneità, generano forme e modi dell'abitare spesso inaspettati.
Così per i territori di Termoli, di Campobasso e di Isernia-Venafro i tanti segni dei "paesaggi del mutamento" restituiscono la molteplicità degli ambienti insediativi esistenti e contribuiscono ad articolare l'immagine e il senso del Molise attuale
MOLISE: L’ANTICA RETE DEI TRATTURI E L’INSEDIAMENTO ANTROPICO ATTUALE. Le trasformazioni del sistema insediativo dalla fine della transumanza alle recenti realizzazioni infrastrutturali.
No full textDa lungo tempo l'immagine prevalente del Molise è quella di uno spazio geografico compatto con caratteri omogenei. Questa immagine, utilizzata come riferimento per politiche territoriali e di realizzazione di grandi opere, oggi non appare più adatta di fronte alla varietà e alla complessità che vanno assumendo le forme del territorio regionale.
Qesta pubblicazione, prodotta nell'ambito della ricerca ITATeN, intende mettere in evidenza alcune differenze emergenti, identificando aree caratterizzate da specifici processi economico-produttivi e da specifiche morfologie insediative.
L'attenzione si rivolge in particolare, agli insediamenti insediativi locali dove i segni del paesaggio storico e naturale combinati con quelli della contemporaneità, generano forme e modi dell'abitare spesso inaspettati.
Così per i territori di Termoli, di Campobasso e di Isernia-Venafro i tanti segni dei "paesaggi del mutamento" restituiscono la molteplicità degli ambienti insediativi esistenti e contribuiscono ad articolare l'immagine e il senso del Molise attuale
Enantioconvergent transformation of racemic cis-beta-alkyl substituted styrene oxides to (R,R) threo diels by microsomal epoxide hydrolase catalysed hydrolysis
No full textBoth enantiomers of cis-beta-ethyl, beta-n-propyl, beta-n-butyl, and beta-n-hexyl substituted styrene oxides undergo microsomal epoxide hydrolase catalysed hydration at the (S) carbon to give the corresponding (R,R) three diols in a > 90% e.e. A complete kinetic resolution of the racemic epoxide is also obtained with the beta-ethyl substituted substrate, but not with its higher homologues
Deracemization of (+/-)-cis-dialkyl substituted oxides via enantioconvergent hydrolysis catalysed by microsomal epoxide hydrolase
No full textBoth enantiomers of cis-(+/-)-2,3-epoxyheptane 1a, cis-3,4-epoxyheptane 1b, cis-3,4-epoxynonane 1c, cis-3,4-epoxynonane-1-ol Id, and cis-1-methoxy-3,4-epoxynonane le undergo a highly stereoselective microsomal epoxide hydrolase catalysed hydration at the (S) carbon to give the corresponding three (R,R)-diol at complete conversion. A total kinetic resolution of racemic epoxides is also obtained with la and 1e. (C) 1998 Elsevier Science Ltd. All rights reserved
SUBSTRATE ENANTIOSELECTIVITY IN THE RABBIT LIVER MICROSOMAL EPOXIDE HYDROLASE CATALYZED-HYDROLYSIS OF TRANS AND CIS 1-PHENYLPROPENE OXIDES - A COMPARISON WITH STYRENE OXIDE
No full textA preferential consumption of the (IS,2S) enantiomer of (+/-)-trans-1-phenylpropene oxide (3) and of the (1R,2S) enantiomer of cis-1-phenylpropene oxide (5) is observed during the rabbit liver mEH catalyzed hydrolysis of these epoxides. This preference is, respectively, much lower and much higher than that found for the consumption of the (R) enantiomer in the hydrolysis of (+/-)-styrene oxide. These results are rationalized in terms of the K(M) and V(max) of the respective reactions
ENANTIOSELECTIVITY IN THE RABBIT LIVER MICROSOMAL BIOTRANSFORMATION OF STYRENE AND PHENYLPROPENES
No full textThe rabbit liver microsomal P-450 catalyzed oxidation of styrene (1a) and isomeric phenylpropenes, trans-1-phenylpropene (1b), cis-1-phenylpropene (1c) and 3-phenylpropene (1d), was investigated and the enantioselectivity of the epoxidation of the olefinic double bond was determined by checking the enantiomeric excesses of the corresponding first formed epoxides (2). These enantiomeric excesses were always modest, ranging between 7% of (1S,2S)-(2b) and 22% of (1R,2R)-(2c). In the case of (1d) a non-enantioselective hydroxylation at the benzylic-allylic C(3) was also observed. The ratio between this hydroxylation and olefin epoxidation of (1d) was 1:2
Enantioconvergent transformation of racemic cis-dialkyl substituted epoxides to (R,R) threo diols by microsomal epoxide hydrolase catalysed hydrolysis
No full textBoth enantiomers of (+/-)-9,10-epoxystearic acid (1b), cis-(+/-)-5,6-epoxyhexadecane (1c) and cis-(+/-)-11,12-epoxyhexadecan-1-ol (1d) as well as the meso cis-9,10-epoxyoctadecane (1a) undergo microsomal epoxide hydrolase catalyzed hydration at the (S) carbon to give the corresponding (R,R) threo diols in a >90 e.e. Copyright (C) 1996 Elsevier Science Lt
DIFFERENT ENANTIOSELECTIVITY AND REGIOSELECTIVITY OF THE CYTOSOLIC AND MICROSOMAL EPOXIDE HYDROLASE CATALYZED-HYDROLYSIS OF SIMPLE PHENYL-SUBSTITUTED EPOXIDES
No full textThe cytosolic (cEH) and the microsomal epoxide hydrolase (mEH) hydrolyse styrene oxide and trans-1-phenylpropene oxide with different enantioselectivity and regioselectivity. While mEH always leads to a regiospecific and enantioselective opening at the non-benzylic oxirane carbon, cEH gives a non-regioselective and non-enantioselective attack to styrene oxide and a regiospecific and non-enantioselective snack at the benzylic carbon of 1-phenylpropene oxide
THE RABBIT LIVER MICROSOMAL BIOTRANSFORMATION OF 1,1-DIALKYLETHYLENES - ENANTIOFACE SELECTION OF EPOXIDATION AND ENANTIOSELECTIVITY OF EPOXIDE HYDROLYSIS
No full textThe rabbit liver microsomal biotransformation of alpha-methylstyrene (1a), 2-methyl-1-hexene (1b), 2,4,4-trimethyl-1-pentene (1c), and 2,3,3-trimethyl-1-butene (1d) has been investigated with the aim at establishing the enantioface selection of the cytochrome P-450-promoted epoxidation of the double bond and the enantioselectivity of microsomal epoxide hydrolase (mEH)-catalyzed hydrolysis of the resulting epoxides. GLC on a Chiraldex G-TA (ASTEC) column was used to determine the enantiomeric composition of the products. The epoxides 2 first produced in incubations carried out in the presence of an NADPH regenerating system were not detected, being rapidly hydrolyzed by mEH to diols 3. The enantiomeric composition of the latter showed that no enantioface selection occurred in the epoxidation of 1c and 1d, and a very low (8%) ee of the (R)-epoxide was formed from 1b. Incubation of racemic epoxides 2b-d with the microsomal fraction showed that the mEH-catalyzed hydrolysis of 2c and 2d was practically nonenantioselective, while that of 2b exhibited a selectivity E = 4.9 favoring the hydrolysis of the (S)-enantiomer. A comparison of these results with those previously obtained for linear and branched chain alkyl monosubstituted oxiranes shows that the introduction of the second alkyl substituent suppresses the selectivity of the mEH reaction of the latter and reverses that of the former substrates. (C) 1994 Wiley-Liss, Inc
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