References of "DelFiore, Guy"
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See detailModulation of brain activity during phonological familiarization
Majerus, Steve ULg; Van der Linden, Martial ULg; Collette, Fabienne ULg et al

in Brain & Language (2005), 92(3), 320-331

We measured brain activity in 12 adults for the repetition of auditorily presented words and nonwords, before and after repeated exposure to their phonological form. The nonword phoneme combinations were ... [more ▼]

We measured brain activity in 12 adults for the repetition of auditorily presented words and nonwords, before and after repeated exposure to their phonological form. The nonword phoneme combinations were either of high (HF) or low (LF) phonotactic frequency. After familiarization, we observed, for both word and nonword conditions, decreased activation in the left posterior superior temporal gyrus, in the bilateral temporal pole and middle temporal gyri. At the same time, interaction analysis showed that the magnitude of decrease of activity in bilateral posterior temporal lobe was significantly smaller for LF nonwords, relative to words and HF nonwords. Decrease of activity in this area also correlated with the size of behavioral familiarization effects for LF nonwords. The results show that the posterior superior temporal gyrus plays a fundamental role during phonological learning. Its relationship to sublexical and lexical phonological processing as well as to phonological short-term memory is discussed. (c) 2004 Elsevier Inc. All rights reserved. [less ▲]

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See detailNeural correlates of "hot" and "cold" emotional processing : a multilevel approach to the functional anatomy of emotion
Schaefer, Alexandre; Collette, Fabienne ULg; Philippot, Pierre et al

in Neuroimage (2003), 18(4), 938-949

The neural correlates of two hypothesized emotional processing modes, i.e., schematic and propositional modes, were investigated with positron emission tomography. Nineteen subjects performed an emotional ... [more ▼]

The neural correlates of two hypothesized emotional processing modes, i.e., schematic and propositional modes, were investigated with positron emission tomography. Nineteen subjects performed an emotional mental imagery task while mentally repeating sentences linked to the meaning of the imagery script. In the schematic conditions, participants repeated metaphoric sentences, whereas in the propositional conditions, the sentences were explicit questions about specific emotional appraisals of the imagery scenario. Five types of emotional scripts were proposed to the subjects (happiness, anger, affection, sadness, and a neutral scenario). The results supported the hypothesized distinction between schematic and propositional emotional processing modes. Specifically, schematic mode was associated with increased activity in the ventromedial prefrontal cortex whereas propositional mode was associated with activation of the anterolateral prefrontal cortex. In addition, interaction analyses showed that schematic versus propositional processing of happiness (compared with the neutral scenario) was associated with increased activity in the ventral striatum whereas "schematic anger" was tentatively associated with activation of the ventral pallidum. (C) 2003 Elsevier Science (USA). All rights reserved. [less ▲]

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See detailA PET investigation of lexicality and phonotactic frequency in oral language processing
Majerus, Steve ULg; Collette, Fabienne ULg; Van der Linden, Martial ULg et al

in Cognitive Neuropsychology (2002), 19(4), 343-360

Lexicality and phonotactic frequency effects are observed in many cognitive studies on language processing, but little is known about their underlying neural substrates, especially with regard to ... [more ▼]

Lexicality and phonotactic frequency effects are observed in many cognitive studies on language processing, but little is known about their underlying neural substrates, especially with regard to phonotactic frequency effects. Here, we conducted a positron emission tomography (PET) study in which 11 right-handed volunteers had either to repeat or to listen to lists of words, high phonotactic frequency nonwords, and low phonotactic frequency nonwords. The comparison of word versus nonword processing consistently confirmed previous findings of left temporal and prefrontal activations classically ascribed to lexicosemantic processing. Higher activation was found in the right posterior superior temporal gyrus when comparing high phonotactic frequency nonwords to words, but not when comparing low phonotactic frequency nonwords to words. We propose that this region is implicated in the formation of temporary phonological representations for high-probability phonological events, which may support processing of high phonotactic frequency nonwords [less ▲]

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See detailGeneration of rapid eye movements during paradoxical sleep in humans
Peigneux, Philippe ULg; Laureys, Steven ULg; Fuchs, Sonia et al

in NeuroImage (2001), 14(3), 701-708

Although rapid eye movements (REMs) are a prominent feature of paradoxical sleep (PS), their origin and functional significance remain poorly understood in humans. In animals, including nonhuman primates ... [more ▼]

Although rapid eye movements (REMs) are a prominent feature of paradoxical sleep (PS), their origin and functional significance remain poorly understood in humans. In animals, including nonhuman primates, REMs during PS are closely related to the occurrence of the so-called PGO waves, i.e., prominent phasic activities recorded throughout the brain but predominantly and most easily in the pons (P), the lateral geniculate bodies (G), and the occipital cortex (O). Therefore, and because the evolution of species is parsimonious, a plausible hypothesis would be that during PS in humans, REMs are generated by mechanisms similar to PGO waves. Using positron emission tomography and iterative cerebral blood flow measurements by H(2)(15)O infusions, we predicted that the brain regions where the PGO waves are the most easily recorded in animals would be differentially more active in PS than in wakefulness, in relation with the density of the REM production [i.e., we looked for the condition (PS versus wakefulness) by performance (REM density) interaction]. Accordingly, we found a significant interaction effect in the right geniculate body and in the primary occipital cortex. The result supports the hypothesis of the existence of processes similar to PGO waves in humans, responsible for REM generation. The interest in the presence of PGO waves in humans is outstanding because the cellular processes involved in, or triggered by, PGO waves might favor brain plasticity during PS. [less ▲]

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See detailThe functional anatomy of inhibition processes investigated with the Hayling task
Collette, Fabienne ULg; Van der Linden, Martial ULg; Delfiore, Guy et al

in Neuroimage (2001), 14(2), 258-267

The cortical areas involved in inhibition processes were examined with positron emission tomography (PET). The tasks administered to subjects were an adaptation of the Hayling test. In the first condition ... [more ▼]

The cortical areas involved in inhibition processes were examined with positron emission tomography (PET). The tasks administered to subjects were an adaptation of the Hayling test. In the first condition (response initiation), subjects had to complete sentences with a word clearly suggested by the context, whereas in the second condition (response inhibition), subjects had to produce a word that made no sense in the context of the sentence. Results indicated that the response initiation processes were associated to increases of activity in the left inferior frontal gyrus (BA 45/47), whereas response inhibition processes led to increases in a network of left prefrontal areas, including the middle (BA 9 and BA 10) and inferior (BA 45) frontal areas. [less ▲]

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See detailContribution of Lexico-Semantic Processes to Verbal Short-Term Memory Tasks: A Pet Activation Study
Collette, Fabienne ULg; Majerus, Steve ULg; Van der Linden, Martial ULg et al

in Memory (2001), 9(4-6), 249-259

Recent studies have demonstrated the intervention of long-term memory processes in verbal STM tasks and several cognitive models have been proposed to explain these effects. A PET study was performed in ... [more ▼]

Recent studies have demonstrated the intervention of long-term memory processes in verbal STM tasks and several cognitive models have been proposed to explain these effects. A PET study was performed in order to determine whether supplementary cerebral areas are involved when subjects have to execute short-term memory tasks for items having representations in long-term memory (in comparison to items without such representations: words vs non-words). Results indicate that verbal STM for words specifically involves the left middle temporal gyrus (BA 21) and temporo-parietal junction (BA 39). These areas can be associated with lexical and semantic processes. These results are in agreement with cognitive models that postulate the simultaneous influence of lexical and semantic long-term representations on verbal STM processes and/or a lexico-semantic buffer. [less ▲]

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See detailStriatum forever, despite sequence learning variability : A random effect analysis of PET data
Peigneux, Philippe ULg; Maquet, Pierre ULg; Meulemans, Thierry ULg et al

in Human Brain Mapping (2000), 10(4), 179-194

This PET study is concerned with the what, where, and how of implicit sequence learning. In contrast with previous studies imaging the serial reaction time (SRT) task, the sequence of successive locations ... [more ▼]

This PET study is concerned with the what, where, and how of implicit sequence learning. In contrast with previous studies imaging the serial reaction time (SRT) task, the sequence of successive locations was determined by a probabilistic finite-state grammar. The implicit acquisition of statistical relationships between serially ordered elements (i.e., what) was studied scan by scan, aiming to evidence the brain areas (i.e., where) specifically involved in the implicit processing of this core component of sequential higher-order knowledge. As behavioural results demonstrate between- and within-subjects variability in the implicit acquisition of sequential knowledge through practice, functional PET data were modelled using a random-effect model analysis (i.e., how) to account for both sources of behavioural variability. First, two mean condition images were created per subject depending on the presence or not of implicit sequential knowledge at the time of each of the 12 scans. Next, direct comparison of these mean condition images provided the brain areas involved in sequential knowledge processing. Using this approach, we have shown that the striatum is involved in more than simple pairwise associations and that it has the capacity to process higher-order knowledge. We suggest that the striatum is not only involved in the implicit automatization of serial information through prefrontal cortex-caudate nucleus networks, but also that it plays a significant role for the selection of the most appropriate responses in the context created by both the current and previous stimuli, thus contributing to better efficiency and faster response preparation in the SRT task. Hum. Brain Mapping 10:179-194, 2000. © 2000 Wiley-Liss, Inc. [less ▲]

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See detailNeural mechanisms of antinociceptive effects of hypnosis.
Faymonville, Marie ULg; Laureys, Steven ULg; Degueldre, Christian ULg et al

in Anesthesiology (2000), 92(5), 1257-67

BACKGROUND: The neural mechanisms underlying the modulation of pain perception by hypnosis remain obscure. In this study, we used positron emission tomography in 11 healthy volunteers to identify the ... [more ▼]

BACKGROUND: The neural mechanisms underlying the modulation of pain perception by hypnosis remain obscure. In this study, we used positron emission tomography in 11 healthy volunteers to identify the brain areas in which hypnosis modulates cerebral responses to a noxious stimulus. METHODS: The protocol used a factorial design with two factors: state (hypnotic state, resting state, mental imagery) and stimulation (warm non-noxious vs. hot noxious stimuli applied to right thenar eminence). Two cerebral blood flow scans were obtained with the 15O-water technique during each condition. After each scan, the subject was asked to rate pain sensation and unpleasantness. Statistical parametric mapping was used to determine the main effects of noxious stimulation and hypnotic state as well as state-by-stimulation interactions (i.e., brain areas that would be more or less activated in hypnosis than in control conditions, under noxious stimulation). RESULTS: Hypnosis decreased both pain sensation and the unpleasantness of noxious stimuli. Noxious stimulation caused an increase in regional cerebral blood flow in the thalamic nuclei and anterior cingulate and insular cortices. The hypnotic state induced a significant activation of a right-sided extrastriate area and the anterior cingulate cortex. The interaction analysis showed that the activity in the anterior (mid-)cingulate cortex was related to pain perception and unpleasantness differently in the hypnotic state than in control situations. CONCLUSIONS: Both intensity and unpleasantness of the noxious stimuli are reduced during the hypnotic state. In addition, hypnotic modulation of pain is mediated by the anterior cingulate cortex. [less ▲]

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See detailThe role of lateral occipitotemporal junction and area MT/V5 in the visual analysis of upper-limb postures
Peigneux, Philippe ULg; Salmon, Eric ULg; Van der Linden, Martial ULg et al

in Neuroimage (2000), 11(6), 644-655

Humans, like numerous other species, strongly rely on the observation of gestures of other individuals in their everyday life. It is hypothesized that the visual processing of human gestures is sustained ... [more ▼]

Humans, like numerous other species, strongly rely on the observation of gestures of other individuals in their everyday life. It is hypothesized that the visual processing of human gestures is sustained by a specific functional architecture, even at an early prelexical cognitive stage, different from that required for the processing of other visual entities. In the present PET study, the neural basis of visual gesture analysis was investigated with functional neuroimaging of brain activity during naming and orientation tasks performed on pictures of either static gestures (upper-limb postures) or tridimensional objects. To prevent automatic object-related cerebral activation during the visual processing of postures, only intransitive postures were selected, i.e., symbolic or meaningless postures which do not imply the handling of objects. Conversely, only intransitive objects which cannot be handled were selected to prevent gesture-related activation during their visual processing. Results clearly demonstrate a significant functional segregation between the processing of static intransitive postures and the processing of intransitive tridimensional objects. Visual processing of objects elicited mainly occipital and fusiform gyrus activity, while visual processing of postures strongly activated the lateral occipitotemporal junction, encroaching upon area MT/V5, involved in motion analysis. These findings suggest that the lateral occipitotemporal junction, working in association with area MT/V5, plays a prominent role in the high-level perceptual analysis of gesture, namely the construction of its visual representation, available for subsequent recognition or imitation. (C) 2000 Academic Press. [less ▲]

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See detailFunctional neuroanatomy of hypnotic state
Maquet, Pierre ULg; Faymonville, Marie-Elisabeth ULg; Degueldre, Christian ULg et al

in Biological Psychiatry (1999), 45(3), 327-333

BACKGROUND: The aim of the present study was to describe the distribution of regional cerebral blood flow during the hypnotic state (HS) in humans, using positron-emission tomography (PET) and statistical ... [more ▼]

BACKGROUND: The aim of the present study was to describe the distribution of regional cerebral blood flow during the hypnotic state (HS) in humans, using positron-emission tomography (PET) and statistical parametric mapping. METHODS: The hypnotic state relied on revivification of pleasant autobiographical memories and was compared to imaging autobiographical material in "normal alertness." A group of 9 subjects under polygraphic monitoring received six H215O infusions and was scanned in the following order: alert-HS-HS-HS with color hallucination-HS with color hallucination-alert. PET data were analyzed using statistical parametric mapping (SPM95). RESULTS: The group analysis showed that hypnotic state is related to the activation of a widespread, mainly left-sided, set of cortical areas involving occipital, parietal, precentral, premotor, and ventrolateral prefrontal cortices and a few right-sided regions: occipital and anterior cingulate cortices. CONCLUSIONS: The pattern of activation during hypnotic state differs from those induced in normal subjects by the simple evocation of autobiographical memories. It shares many similarities with mental imagery, from which it differs by the relative deactivation of precuneus. [less ▲]

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See detailRegional brain activity during tasks devoted to the central executive of working memory
Collette, Fabienne ULg; Salmon, Eric ULg; Van der Linden, Martial ULg et al

in Cognitive Brain Research (1999), 7(3), 411-417

Most previous PET studies investigating the central executive (CE) component of working memory found activation in the prefrontal cortex. However, the tasks used did not always permit to distinguish ... [more ▼]

Most previous PET studies investigating the central executive (CE) component of working memory found activation in the prefrontal cortex. However, the tasks used did not always permit to distinguish precisely the functions of the CE from the storage function of the slave systems. The aim of the present study was to isolate brain areas that subserve manipulation of information by the CE when the influence of storage function was removed. A PET activation study was performed with four cognitive tasks, crossing conditions of temporary storage and manipulation of information. The manipulation of information induced an activation in the right (BA 10/46) and left (BA 9/6) middle frontal gyrus and in the left parietal area (BA7). The interaction between the storage and manipulation conditions did not reveal any significant changes in activation. These results are in agreement with the hypothesis that CE functions are distributed between anterior and posterior brain areas, but could also reflect a simultaneous involvement of controlled (frontal) and automatic (parietal) attentional systems. In the other hand, the absence of interaction between the storage and manipulation conditions demonstrates that the CE is not necessarily related to the presence of a memory load. [less ▲]

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See detailLeft inferior frontal cortex is involved in probabilistic serial reaction time learning
Peigneux, Philippe ULg; Maquet, Pierre ULg; Van der Linden, Martial ULg et al

in Brain and Cognition (1999), 40(1), 215-219

Cerebral blood flow was estimated using positron emission tomography and H2O15 infusions in 12 volunteers while they were trained on the probabilistic serial reaction time task developed by Jimenez ... [more ▼]

Cerebral blood flow was estimated using positron emission tomography and H2O15 infusions in 12 volunteers while they were trained on the probabilistic serial reaction time task developed by Jimenez, Mender, and Cleeremans (1996). Participants' reaction rimes to predictable and nonpredictable stimuli showed increasing sensitivity to the: probabilistic constraints set by previous elements of the sequence. Analysis by statistical parametric mapping showed a significant interaction between participants' performance and time effect in the left inferior frontal cortex. Our results provide the first evidence of this cerebral area being involved in the processing of contextual information in a probabilistic sequence learning task. [less ▲]

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See detailThe neural correlates of updating information in verbal working memory
Van der Linden, Martial ULg; Collette, Fabienne ULg; Salmon, Eric ULg et al

in Memory (1999), 7(5-6), 549-560

The aim of the present study was to re-examine cerebral areas subserving the updating function of the central executive with a running span task requiring subjects to watch strings of consonants of ... [more ▼]

The aim of the present study was to re-examine cerebral areas subserving the updating function of the central executive with a running span task requiring subjects to watch strings of consonants of unknown length and then to recall serially a specific number of recent items. In order to dissociate more precisely the updating process from the storage function, a four-item instead of a six-item memory load was used, contrary to our previous study (Salmon et al., 1996). In addition, a serial recall procedure was preferred to a recognition procedure in order to suppress the use of visuospatial strategies. The most significant increase of rCBF occurred in the left frontopolar cortex (Brodmann's area 10), spreading to the left middle frontal (Brodmann's area 46). Results suggest that frontopolar activation underlies an updating process in working memory. [less ▲]

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See detailRegional brain activity during working memory tasks
Salmon, Eric ULg; Van der Linden, Martial ULg; Collette, Fabienne ULg et al

in Brain (1996), 119(Pt 5), 1617-1625

The first aim of our PET study was to replicate previous findings concerning the brain areas activated by a verbal working memory task. The second aim was to specify the neural basis of the central ... [more ▼]

The first aim of our PET study was to replicate previous findings concerning the brain areas activated by a verbal working memory task. The second aim was to specify the neural basis of the central executive, using a task of working memory updating. Our data confirm that the lower left supramarginal gyms and premotor area are the key regions subserving short-term verbal memory processes. They also suggest that the updating memory task is related to mid-dorsolateral prefrontal activation most probably responsible for the updating function of the central executive. An unexpected, predominantly right activation occurred in the inferior parietal region during the verbal memory updating task, which we related to a visuospatial strategy used to maintain the information in short-term memory. A third purpose was to explore the brain regions activated by a nonverbal, visual memory task, and our results confirm the importance of the superior occipital gyrus in the visual short-term memory. [less ▲]

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See detailCombined study of cerebral glucose metabolism and [11C] methionine accumulation in probable Alzheimer's disease using positron emission tomography
Salmon, Eric ULg; Grégoire, M. C.; Delfiore, Guy et al

in Journal of Cerebral Blood Flow & Metabolism (1996), 16(3), 399-408

There is a characteristic decrease in glucose metabolism in associative frontal and temporo-parietal cortices of patients suffering from Alzheimer's disease (AD). The decrease in metabolism might result ... [more ▼]

There is a characteristic decrease in glucose metabolism in associative frontal and temporo-parietal cortices of patients suffering from Alzheimer's disease (AD). The decrease in metabolism might result from local neuronal loss or from a decrease of synaptic activity. We measured in vivo [11C]methionine accumulation into proteins with positron emission tomography (PET) to assess cortical tissue loss in AD. Both global regional activity and compartmental analysis were used to express [11C]methionine accumulation into brain tissue. Glucose metabolism was measures with [18F]fluorodeoxyglucose and autoradiographic method. Combined studies were performed in 10 patients with probable AD, compared to age-matched healthy volunteers. There was a significant 45% decrease of temporo-parietal glucose metabolism in patients with AD, and frontal metabolism was lowered in most patients. Temporo-parietal metabolism correlated to dementia severity. [11C]methionine incorporation into temporo-parietal and frontal cortices was not significantly decreased in AD. There was no correlation with clinical symptoms. Data suggest that regional tissue loss, assessed by the decrease of [11C]methionine accumulation, is not sufficient to explain cortical glucose hypometabolism, which reflects, rather, reduced synaptic connectivity. [less ▲]

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See detailBrain activation induced by estimation of duration : A PET study
Maquet, Pierre ULg; Lejeune, Helga ULg; Pouthas, V. et al

in Neuroimage (1996), 3(2), 119-126

Duration information about a visual stimulus requires processing as do other visual features such as size or intensity. Using positron emission tomography, iterative (H2O)-O-15 infusions, and statistical ... [more ▼]

Duration information about a visual stimulus requires processing as do other visual features such as size or intensity. Using positron emission tomography, iterative (H2O)-O-15 infusions, and statistical parametric mapping, we investigated the neural correlates of time processing. Nine normal subjects underwent six serial rCBF. Three tasks were studied: (a) Atemporal generalization task (D task) in which the subjects had to judge (by pressing one of two keys) whether the duration of the illumination of a green LED was equal to or different from that of a previously presented standard; (b) An intensity generalization task. (I task) in which the judgment concerned the intensity of the LED; and (c) A control task (C task) in which the subjects had to press one of the two keys at random in response to LED illumination. A significant increase in rCBF during the D task, compared to that during the C task, was observed in right prefontal cortex, right inferior parietal lobule, anterior cingulate cortex, vermis, and a region corresponding to the left fusiform gyrus. A significant increase in rCBF during the I task, compared to that during the C task, was observed in right prefontal cortex, right inferior parietal lobule, right extrastriate cortex, anterior cingulate cortex, left inferior parietal lobule, vermis, and two symmetrical regions corresponding to the fusiform gyri. No significant activation was observed in the D task when compared to that in the I task. We propose that these cortical maps are best explained by the recruitment of visual attention and memory structures, which play a major role in prospective time judgements as indicated by behavioral studies. The data also suggest that the temporal dimension of a visual stimulus is processed in attributes. the same areas as other visual attributes. [less ▲]

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See detailENANTIOSELECTIVE SYNTHESES OF NCA (S)-L-[BETA-C-11]-4-CHLOROPHENYLALANINE AND (S)-L-(ALPHA-METHYL)-[BETA-C-11]-4-CHLOROPHENYLALANINE
Plenevaux, Alain ULg; Al-Darwich, M. J.; Lemaire, Christian ULg et al

in Applied Radiation & Isotopes (1994), 45(3), 361-369

The radiolabeling of (S)-L-4-chlorophenylalanine and (S)-L-(alpha-methyl)-4-chlorophenylalanine were realized with carbon-11 at position beta through a radiochemical synthesis relying on the highly ... [more ▼]

The radiolabeling of (S)-L-4-chlorophenylalanine and (S)-L-(alpha-methyl)-4-chlorophenylalanine were realized with carbon-11 at position beta through a radiochemical synthesis relying on the highly enantioselective reaction between 4-chloro[alpha-C-11]benzyl bromide and the lithium enolate of (S)-1-(t-butyloxycarbonyl)-2-(t-butyl)-3-methyl-1,3-imidazolidine-4-one for (S)-L-[beta-C-11]-4-chlorophenylalanine and of (2S,5S)-1-(t-butyloxycarbonyl)-2-(t-butyl)-3,5-dimethyl-1,3-imidazolidin e-4-one for (S)-L-(alpha-methyl)-[beta-C-11]-4-chlorophenylalanine. Quantities of about 25-35 mCi were obtained at the end of synthesis, ready for injection, after hydrolysis and HPLC purification with a radiochemical yield of 19% corrected to EOB within 45 min. The enantiomeric excesses were shown to be greater than or equal to 97% for both molecules without chiral separation. The radiochemical and the chemical purities of the final compounds were greater than or equal to 98% and the specific activity at the end of synthesis ranged between 250-800 mCi/mu mol. [less ▲]

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See detailENANTIOSELECTIVE SYNTHESIS OF NCA (S)-L-([ALPHA-C-11]METHYL)-TRYPTOPHAN
Plenevaux, Alain ULg; Lemaire, Christian ULg; Delfiore, Guy et al

in Applied Radiation & Isotopes (1994), 45(6), 651-653

N.c.a. (S)-L-([alpha-C-11]methyl)-tryptophan was prepared by treatment at -78-degrees-C of (2S,3aR,8aS)-1,2-bis(-methoxycarbonyl)-1,2,3,3a,8,8a-hexahydropyrrolo[2, 3-b]-indole with lithium ... [more ▼]

N.c.a. (S)-L-([alpha-C-11]methyl)-tryptophan was prepared by treatment at -78-degrees-C of (2S,3aR,8aS)-1,2-bis(-methoxycarbonyl)-1,2,3,3a,8,8a-hexahydropyrrolo[2, 3-b]-indole with lithium diisopropylamide and [C-11]CH3I. After hydrolysis with HI and HPLC purification, the title compound was isolated with a radiochemical yield of 36% (EOB corrected) within 22 min; e.e. was shown > 97% (n = 20); specific activity was ranging between 0.8 and 1.2 Ci (30-45 GBq)/mu mol EOB. [less ▲]

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