2‐Phenyl‐5‐Oxazolone

VandenBerg, G. E.; Harrison, Jeffrey B.; Carter, H. E.; Magerlein, Barney J.

doi:10.1002/0471264180.os047.32

Cited by 4 publications

(6 citation statements)

References 2 publications

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“…2-Phenyl-5-oxazolone was synthesized in accordance with an established procedure, using hippuric acid as the starting material and acetic anhydride as the solvent [46]. The structure of the oxazolone standard was confirmed using 1 H NMR and mass spectrometry.…”

Section: Synthesis Of 2-phenyl-5-oxazolonementioning

confidence: 99%

Why are a₃ ions rarely observed?

Allen

Racine

Berman

et al. 2008

J. Am. Soc. Mass Spectrom.

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It has been determined experimentally that a 3 ions are generally not observed in the tandem mass spectroscopic (MS/MS) spectra of b 3 ions. This is in contrast to other b n ions, which often have the corresponding a n ion as the base peak in their MS/MS spectra. Although this might suggest a different structure for b 3 ions compared to that of other b n ions, theoretical calculations indicate the conventional oxazolone structure to be the lowest energy structure for the b 3 ion of AAAAR, as it is for other b n ions of this peptide. However, it has been determined theoretically that the a 3 ion is lower in energy than other a n ions, relative to the corresponding b ions. Furthermore, the a 3 ¡ b 2 transition structure (TS) is lower in energy than other a n ¡ b nϪ1 TSs of AAAAR, compared with the corresponding b ions. Consequently, it is suggested that the b 3 ion does fragment to the a 3 ion, but that the a 3 ion then immediately fragments (to b 2 and a 3 *) because of the excess internal energy arising from its relatively low energy and the facile It has been shown that significant rearrangement can occur upon peptide dissociation, particularly in mass spectrometers with relatively long activation/dissociation times such as ion trapping instruments [23][24][25][26][27][28]. However, rearrangements are not limited to ion trapping mass spectrometers [29 -32]. In actuality even b and y ions are formed by rearrangements involving hydrogen atom transfers (y ions) or intramolecular cyclization (b ions). The ubiquitousness of the mechanism for formation of b and y ions has been shown through kinetic energy loss measurements [33].Initially it was thought that b ions had a simple acylium ion structure [5,34,35]. However, this theory was discredited because b 1 ions are not often observed in MS/MS spectra (i.e., these ions should also be acylium ions by the preceding rationale). The current consensus is that b ions most commonly have a protonated oxazolone structure [36 -39]. This has been demonstrated in gas-phase IR studies on the b 4 ions of YGGFL [38,40]. Additionally, recent experimental and theoretical data suggest that larger oxazolones can undergo head-to-tail cyclization to form cyclic-peptide isomers [32,40]. Further evidence supporting the conclusion that b ions have the protonated oxazolone structure is that the major dissociation products of b ions (a n and b nϪ1 ions) have product ion analogs in the MS/MS spectra of synthesized oxazolone compounds [37].Although formation of a n ions via the b n ¡ a n pathway is well understood [41], the actual mechanism of b nϪ1 formation is less clear. Two major mechanisms were considered here, the direct b n ¡ b nϪ1 [36] and indirect b n ¡ a n ¡ b nϪ1 [42] pathways. Metastable ion studies indicate that a n ions are formed with substantial release of kinetic energy (KER). On the other hand b nϪ1 fragments are formed from b n parents with small KER values [36,37]. This finding suggests that a direct b n ¡ b nϪ1 mechanism is preferred. Additionally, doubleresonance experimen...

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Section: Synthesis Of 2-phenyl-5-oxazolonementioning

confidence: 99%

Why are a₃ ions rarely observed?

Allen

Racine

Berman

et al. 2008

J. Am. Soc. Mass Spectrom.

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“…Instead, we turned our attention to activate the glycine and mercaptoacetic acid units by converting them into 2-phenyl-1,3-oxazol-5-one 2 and 2-methyl-2-phenyl-1,3-oxathiolan-5-one 3, respectively. 11,12 This worked well as the -COOH and -NH 2 or -SH groups of glycine/mercaptoacetic acid were blocked, and their methylene group was activated to act as the Michael donor. 15 As regards the choice of catalyst, we tested several Lewis acids for the synthesis of the representative compound 5 (R = Ph; EWG = NO 2 ) using a water/1,4-dioxane (1:2, v/v) solvent system.…”

Section: Introductionmentioning

confidence: 98%

Direct introduction of glycine/mercaptoacetic acid units into electron-poor alkenes: a novel route to functionally rich α-amino/α-mercapto acids

Yadav

Rai

2008

Tetrahedron Letters

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“…Instead, we turned our attention to block the COOH and NH 2 groups and thus activating its methylene group by converting glycine into 2-phenyl-1,3-oxazol-5-one (2), 8 which works well for the synthesis of N-protected a-amino acids 4 (Scheme 1). Recently, Moorthy and Singhal have described a highly selective conversion of nitriles to amides.…”

mentioning

confidence: 99%

“…8 oxazol-5-one (2, 2 mmol) was added to the reaction mixture, and it was stirred at r.t. for 6-8 h followed by addition of H 2 O (5 mL) and stirring was continued for the next 1-2 h at r.t. (Table 2). After completion of the reaction as indicated by TLC, the solvent was evaporated under reduced pressure, H 2 O (10 mL) was added to the reaction mixture and extracted with CH 2 Cl 2 (3 × 10 mL), the combined organic phase concentrated under reduced pressure, and the crude product 4 thus obtained was recrystallized from EtOH to afford a diastereomeric mixture (>92:<8; in the crude products the ratio was >90:<10 as determined by 1 H NMR spectroscopy).…”

mentioning

confidence: 99%

A Novel One-Pot Stereoselective Synthesis of N-Protected α-Amino Acids from Morita-Baylis-Hillman Acetates

Yadav¹,

Kumar²,

Singh³

2009

Synlett

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The first example of an operationally simple direct regioand diastereoselective introduction of N-protected a-amino acids into Morita-Baylis-Hillman (MBH) acetates is reported. The DABCO-catalyzed reaction of MBH acetates with 2-phenyl-1,3-oxazol-5-one affords N-protected a-amino acids regioselectively in excellent yield (81-93%) with high diastereoselectivity (>92%) at ambient temperature. The synthetic protocol involves S N 2¢-S N 2¢ reaction and water-driven ring-opening cascades in a one-pot procedure, which are salient features of the present investigation.

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2‐Phenyl‐5‐Oxazolone

Abstract: 2‐Phenyl‐5‐oxazolone solvent: Skellysolve B product: 2‐phenyl‐5‐oxazolone

Cited by 4 publications

References 2 publications

Why are a₃ ions rarely observed?

Why are a₃ ions rarely observed?

Direct introduction of glycine/mercaptoacetic acid units into electron-poor alkenes: a novel route to functionally rich α-amino/α-mercapto acids

A Novel One-Pot Stereoselective Synthesis of N-Protected α-Amino Acids from Morita-Baylis-Hillman Acetates

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2‐Phenyl‐5‐Oxazolone

Abstract: 2‐Phenyl‐5‐oxazolone solvent: Skellysolve B product: 2‐phenyl‐5‐oxazolone

Cited by 4 publications

References 2 publications

Why are a3 ions rarely observed?

Why are a3 ions rarely observed?

Direct introduction of glycine/mercaptoacetic acid units into electron-poor alkenes: a novel route to functionally rich α-amino/α-mercapto acids

A Novel One-Pot Stereoselective Synthesis of N-Protected α-Amino Acids from Morita-Baylis-Hillman Acetates

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Product

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Why are a₃ ions rarely observed?

Why are a₃ ions rarely observed?