Synthèse et réactivité d′oxazolopipéridines et d'oxazolopipéridones

Alazard, J.-P.; Terrier, Corinne; Mary, Aude; Thal, C.

doi:10.1016/s0040-4020(01)80648-7

Cited by 6 publications

(4 citation statements)

References 13 publications

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“…The above results can be rationalized by taking into account that, after the formation of the corresponding oxazolidines, lactamization occurs faster through a chair‐like transition state in which the diastereotopic acetate (R 3 in Scheme 5) or propionate chain (R 2 in Scheme 5) that does not undergo cyclization is equatorial. In accordance with this interpretation, the presence of an ethyl substituent at the prochiral carbon atom in 1 s (R 2 =Et) suppresses the discrimination between the two propionate chains and lactams 9 s and 10 s (9:1 ratio) were formed along with equimolecular amounts of the corresponding C‐8 epimers 9 s′ and 10 s′ 19. In this case, either the ethyl substituent or one of the propionate chains is axially oriented.…”

Section: Resultsmentioning

confidence: 60%

Dynamic Kinetic Resolution and Desymmetrization Processes: A Straightforward Methodology for the Enantioselective Synthesis of Piperidines

Amat

Bassas

Llor

et al. 2006

Chemistry A European J

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A straightforward procedure for the synthesis of enantiopure polysubstituted piperidines is reported. It involves the direct generation of chiral non-racemic oxazolo[3,2-a]piperidone lactams that already incorporate carbon substituents on the heterocyclic ring and the subsequent removal of the chiral auxiliary. The key step is a cyclocondensation reaction of (R)-phenylglycinol or other amino alcohols with racemic or prochiral delta-oxo (di)acid derivatives in highly stereoselective processes involving dynamic kinetic resolution and/or desymmetrization of diastereotopic or enantiotopic ester groups.

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Section: Resultsmentioning

confidence: 60%

Dynamic Kinetic Resolution and Desymmetrization Processes: A Straightforward Methodology for the Enantioselective Synthesis of Piperidines

Amat

Bassas

Llor

et al. 2006

Chemistry A European J

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“…The dynamic model of the spacecraft without the RWA dynamic contribution is obtained thanks to the Satellite Dynamics Toolbox (SDT) [6]. The frequencies of the modes of the solar panels and the antenna are resumed in Table 1.…”

Section: Dynamics Of a Spacecraft With An Rwa Sy-stemmentioning

confidence: 99%

“…The TITOP RWA model is then assembled with the dynamic model of a space telescope with two flexible solar arrays and an antenna obtained by the Satellite Dynamics Toolbox (SDT) [6] in order to analyze the possible coupling effects between the spacecraft structural modes and the flexible modes due to the RWA. In this way it is possible to analyze in which range of frequencies a passive solution can act to reduce the problem of microvibrations to reach the expected performances.…”

Section: Introductionmentioning

confidence: 99%

A Novel Dynamic Model of a Reaction Wheel Assembly for High Accuracy Pointing Space Missions

Sanfedino

Alazard

Pommier-Budinger

et al. 2018

Volume 3: Modeling and Validation; Multi-Agent and Networked Systems; Path Planning and Motion Control; Tracking Control System

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This paper proposes a novel dynamic model of a Reaction Wheel Assembly (RWA) based on the Two-Input Two-Output Port framework, already presented by the authors. This method allows the user to study a complex system with a sub-structured approach: each sub-element transfers its dynamic content to the other sub-elements through local attachment points with any set of boundary conditions. An RWA is modelled with this approach and it is then used to study the impact of typical reaction wheel perturbations on a flexible satellite in order to analyze the microvibration content for a high accuracy pointing mission. This formulation reveals the impact of any structural design parameter and highlights the need of passive isolators to reduce the microvibration issues. The frequency analysis of the transfer between the disturbance sources and the line-of-sight (LOS) jitter highlights the role of the reaction wheel speed on the flexible modes migration and suggests which control strategies can be considered to mitigate the residual micro-vibration content in order to fulfil the mission performances.

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“…Introduction of the (2-nitrophenyl)acetyl group to different carbohydrate derivatives was readily accomplished by conventional methods, using the acid chloride ( 5a ), the previously unreported crystalline anhydride ( 5b ), or the acid ( 5c ) itself in carbodiimide-promoted acylations (Scheme ). Alternatively, the Mitsunobu reaction was also used with the free acid, and it showed a remarkable regioselectivity toward the primary hydroxyl.…”

mentioning

confidence: 99%

(2-Nitrophenyl)acetyl: A New, Selectively Removable Hydroxyl Protecting Group

Daragics

Fügedi

2010

Org. Lett.

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The utility of the (2-nitrophenyl)acetyl (NPAc) group for the protection of hydroxyl functions is reported. (2-Nitrophenyl)acetates are readily prepared starting from the commercially available, inexpensive (2-nitrophenyl)acetic acid, and these esters are stable under a series of common carbohydrate transformations. The NPAc group can be removed selectively using Zn and NH(4)Cl without affecting a series of common protecting groups. This new protecting group is orthogonal with the commonly used tert-butyldimethylsilyl, levulinoyl, 9-fluorenylmethoxycarbonyl, naphthylmethyl, and p-methoxybenzyl groups.

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Synthèse et réactivité d′oxazolopipéridines et d'oxazolopipéridones

Cited by 6 publications

References 13 publications

Dynamic Kinetic Resolution and Desymmetrization Processes: A Straightforward Methodology for the Enantioselective Synthesis of Piperidines

Dynamic Kinetic Resolution and Desymmetrization Processes: A Straightforward Methodology for the Enantioselective Synthesis of Piperidines

A Novel Dynamic Model of a Reaction Wheel Assembly for High Accuracy Pointing Space Missions

(2-Nitrophenyl)acetyl: A New, Selectively Removable Hydroxyl Protecting Group

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