Stereoselective Synthesis of (‐)‐Cytoxazone and (+)‐5‐Epi‐cytoxazone.

Kumar, Amit; Bhaskar, G.; Madhan, A.; Rao, B. Venkateswara

doi:10.1002/chin.200350224

Cited by 2 publications

(7 citation statements)

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“…R f 0.5 (hexane/EtOAc 70:30). [α] D 22 = −93.8° ( c = 1.3, CHCl 3 ) (literature, 9 [α] D 25 = −95.3° [ c = 1.2, CHCl 3 ]). IV (neat):

\overset{v}{true}

max 3375, 2977, 2839, 1743, 1706, 1611, 1586, 1510, 1462, 1438, 1392, 1366, 1305, 1244, 1214, 1158, 1112, 1052, 1028, 914, 894, 852, 832, 797, 781, 763 cm −1 .…”

Section: Methodsmentioning

confidence: 97%

“…The organic phase was washed with brine, dried over Na 2 SO 4 , and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (hexane/EtOAc 85:15), providing ester 3 (94% yield, two steps) as a yellowish solid, mp 65.5-66.6 C (literature, 9 66-67 C). R f 0.5 (hexane/EtOAc 70:30 (10 ml) was added slowly.…”

Section: (R)-2-((tert-butoxycarbonyl)amino)-2-(4-methoxyphenyl)methyl Acetate (3)mentioning

confidence: 99%

“…Of note, Kumar et al 9 found (+)‐5‐ epi ‐cytoxazone (Figure 1) to have higher antibacterial activity than (−)‐cytoxazone against Gram‐positive Bacillus subtilis and Gram‐negative Escherichia coli . The discoveries made by these groups encouraged the development of research aimed at the total synthesis of (−)‐cytoxazone and congeners 5,6,10 …”

Section: Introductionmentioning

confidence: 98%

“…10 Figure 2 shows a compilation of some synthetic protocols as well as the key steps for the construction of the basic skeleton of (À)-cytoxazone and congeners. [7][8][9][11][12][13][14][15][16][17][18][19] Sharpless asymmetric dihydroxylation (Figure 2, route A) using AD-mix-α in t-BuOH/H 2 O was the key step in the control of stereogenic centers at C-4 and C-5 of (À)-cytoxazone, according to Sakamoto et al 7 and Seki and Mori. 8 Carter et al 12 explored the 1,2-syn aldol reaction (Figure 2, route D), starting from chiral imide and an aldehyde and mediated by Bu 2 BOTf, in the development of a new enantioselective synthesis of (À)-cytoxazone.…”

Section: Introductionmentioning

confidence: 99%

“…Their β‐amino acid and α‐hydroxy functionalities are introduced via Sharpless enantioselective epoxidation, hydroxylation, and aminohydroxylation or by means of well‐known (Evans oxazolidinone, N‐tert ‐butanesulfinylimines) and less‐known chirality inducers 10 . Figure 2 shows a compilation of some synthetic protocols as well as the key steps for the construction of the basic skeleton of (−)‐cytoxazone and congeners 7–9,11–19 …”

Section: Introductionmentioning

confidence: 99%

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Stereoselective synthesis of (−)‐cytoxazone and its unnatural congener (+)‐5‐epi‐cytoxazone

et al. 2021

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An interesting protocol for stereoselective synthesis of (À)-cytoxazone and its unnatural stereoisomer (+)-5-epi-cytoxazone from D-4-hydroxyphenylglycine in overall yields of 10% and 16%, respectively, is described. The stereoselective addition of cyanide to an N-Boc protected aminoaldehyde (tert-butyl ((R)-1-(4-methoxyphenyl)-2-oxoethyl)carbamate) (5) constitutes the key step in this approach, producing a mixture of cyanohydrins 6a and b (1,2-anti and 1,2-syn tert-butyl (2-cyano-2-hydroxy-1-(4-methoxyphenyl)ethyl)carbamate) in 89% yield, with reasonable stereoselectivity (1.0:1.8) in favor of the anti-Felkin product (1,2-syn). A one-pot sequence of three successive steps from this mixture produced the oxazolidinone isomers 9a and b ((4R,5R)-and (4R,5S)-4-(4-methoxyphenyl)-2-oxooxazolidine-5-carboxylate). Chromatographic column separation and reduction of the ester function of both precursors led to (À)-cytoxazone and (+)-5-epi-cytoxazone.

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“…R f 0.5 (hexane/EtOAc 70:30). [α] D 22 = −93.8° ( c = 1.3, CHCl 3 ) (literature, 9 [α] D 25 = −95.3° [ c = 1.2, CHCl 3 ]). IV (neat):

\overset{v}{true}

max 3375, 2977, 2839, 1743, 1706, 1611, 1586, 1510, 1462, 1438, 1392, 1366, 1305, 1244, 1214, 1158, 1112, 1052, 1028, 914, 894, 852, 832, 797, 781, 763 cm −1 .…”

Section: Methodsmentioning

confidence: 97%

Section: (R)-2-((tert-butoxycarbonyl)amino)-2-(4-methoxyphenyl)methyl Acetate (3)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Stereoselective synthesis of (−)‐cytoxazone and its unnatural congener (+)‐5‐epi‐cytoxazone

et al. 2021

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Progression of Absolute Configuration Determination in Natural Product Chemistry Using Optical Rotation (Dispersion), Matrix Determinant and Electronic Circular Dichroism Methods

Sheng-Ding¹,

Shen²,

Luo³

et al. 2011

COC

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With the development of separation materials, more and more complex natural products with poly-stereogenic centers are obtained. However, due to small quantity of the isolated compounds, or no crystal formed, or complex 2D NMR correlation signals, absolute configuration identification for these compounds becomes difficult. Now, computational methods provide researchers many benefits in structural determinations for chiral natural products. Computational methods include (1) optical rotation (OR) and its dispersion (ORD) computations; (2) electronic circular dichroism (ECD or CD) calculations; (3) computations of determinant of matrix for stereogenic centers. In methods (1) to (2), the mostly used quantum theory contained density functional theory (DFT) with different basis sets, e.g. B3LYP/aug-cc-pVDZ//B3LYP/6-31G(d). Effects from solvents on OR value can be investigated using different corresponding software. In the cases, optimizations performed in the corresponding solution are helpful to obtain the correct predictions although it is not usual at present time. Matrix model as one of the mathematic methods is different from quantum methods, which is of easily being understood and effective in absolute configuration assignment for acyclic chiral compounds. In this review, necessary theory basis for the three methods are simply introduced for modern readers, the focus of which is the application of these methods in natural product chemistry by various examples reported in different journals from 1998 to the end of April of 2010 except for matrix method to the May of 2010 based on an experimental chemist's viewpoints.

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Stereoselective Synthesis of (‐)‐Cytoxazone and (+)‐5‐Epi‐cytoxazone.

Abstract: For Abstract see ChemInform Abstract in Full Text.

Cited by 2 publications

References 1 publication

Stereoselective synthesis of (−)‐cytoxazone and its unnatural congener (+)‐5‐epi‐cytoxazone

Stereoselective synthesis of (−)‐cytoxazone and its unnatural congener (+)‐5‐epi‐cytoxazone

Progression of Absolute Configuration Determination in Natural Product Chemistry Using Optical Rotation (Dispersion), Matrix Determinant and Electronic Circular Dichroism Methods

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