Asymmetric synthesis of (2S,3S)-3-carboxy-proline

Cotton, Ron; Johnstone, Andrew N.C.; North, Michael

doi:10.1016/s0040-4039(00)78517-0

Cited by 14 publications

(3 citation statements)

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“…Compound 8 could be charge-tagged to 9 using ethyl bromide. Finally, the free catalyst 1 was obtained by acidic deprotection [ 59 ].…”

Section: Resultsmentioning

confidence: 99%

“…4-(4-((3 S ,5 S )-5-Carboxypyrrolidin-3-yloxy)phenyl)-1-ethylpyridinium bromide (1) was prepared analogous to a known procedure [59] and obtained as beige-brown solid (96%). 1 H NMR (400 MHz, CD 3 OD) δ 8.92 (d, 3 J = 6.4 Hz, 2H, H o-py ), 8.37 (d, 3 J = 6.4 Hz, 2H, H m-py ), 8.06 (d, 3 J = 8.6 Hz, 2H, H m-ph ), 7.27/7.20 (d, 3 J = 8.6 Hz, 2H, H o-ph ), 5.42 (s, 1H, CH 2 C H CH 2 ), 4.73–4.58 (m, 3H, C H 2 CH 3 and CH 2 C H N), 3.82–3.62 (m, 2H, NC H 2 CH), 2.85–2.73 (m, 1H, CHC H 2 CH), 2.71–2.63 (m, 1H, CHC H 2 CH), 1.67 (t, 3 J = 7.3 Hz, 3H, CH 2 C H 3 ) ppm; 13 C NMR (100 MHz, CD 3 OD) δ 171.0 ( C ═O), 160.9 ( C ph −O), 156.9 ( C p-py −C), 145.4 ( C o-py −H), 131.0 ( C m-ph -H), 128.5 ( C p-ph -C), 125.2 ( C m-py −H), 118.0 ( C o-ph −H), 77.3/76.7 (CH 2 C HCH 2 ), 59.8 (CH 2 C HN), 57.4 ( C H 2 CH 3 ), 52.7 (N C H 2 CH), 35.7 (CH C H 2 CH), 16.7 (CH 2 C H 3 ) ppm; HRESIMS ( m / z ): [M] + calcd for C 18 H 21 N 2 O 3 , 313.1547; found, 313.1563.…”

Section: Methodsmentioning

confidence: 99%

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A new charge-tagged proline-based organocatalyst for mechanistic studies using electrospray mass spectrometry

Willms¹,

Beel²,

Schmidt³

et al. 2014

Beilstein J. Org. Chem.

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SummaryA new 4-hydroxy-L-proline derivative with a charged 1-ethylpyridinium-4-phenoxy substituent has been synthesized with the aim of facilitating mechanistic studies of proline-catalyzed reactions by ESI mass spectrometry. The charged residue ensures a strongly enhanced ESI response compared to neutral unmodified proline. The connection by a rigid linker fixes the position of the charge tag far away from the catalytic center in order to avoid unwanted interactions. The use of a charged catalyst leads to significantly enhanced ESI signal abundances for every catalyst-derived species which are the ones of highest interest present in a reacting solution. The new charged proline catalyst has been tested in the direct asymmetric inverse aldol reaction between aldehydes and diethyl ketomalonate. Two intermediates in accordance with the List–Houk mechanism for enamine catalysis have been detected and characterized by gas-phase fragmentation. In addition, their temporal evolution has been followed using a microreactor continuous-flow technique.

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“…Compound 8 could be charge-tagged to 9 using ethyl bromide. Finally, the free catalyst 1 was obtained by acidic deprotection [ 59 ].…”

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

A new charge-tagged proline-based organocatalyst for mechanistic studies using electrospray mass spectrometry

Willms¹,

Beel²,

Schmidt³

et al. 2014

Beilstein J. Org. Chem.

View full text Add to dashboard Cite

show abstract

“…Direct alkylation of aspartic acid derivatives was first reported by Seebach in 1981, 2 and later by Baldwin and other workers. [3][4][5][6][7][8][9][10][11][12] Except for reports of stereospecific allylation, 10,11 these reactions gave mixtures of diastereoisomers. A recent study has indicated how the structural and experimental features in such reactions affect the diastereoselectivity.…”

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confidence: 99%