α‐Hydroxy Acids in Enantioselective Syntheses

Coppola, Garry M.; Schuster, Herbert F.

doi:10.1002/352760085x

Cited by 332 publications

(269 citation statements)

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“…The 1 H (500 MHz) and 13 C (125 MHz) NMR data recorded in CD 3 OD were listed in Materials and Method Section, since the data has not been reported thus far. It is known that natural malic acid present in fruits including green apples and other fruits is a (S)-(−) form (Coppola and Schuster 2002), and thus AAL1 can be reasonably assumed to be (S)-malic acid. This was confirmed by the negative sign of the specific optical rotation.…”

Section: Resultsmentioning

confidence: 99%

Antioxidant property and α $$ \boldsymbol{\upalpha} $$ -glucosidase, α $$ \boldsymbol{\upalpha} $$ -amylase and lipase inhibiting activities of Flacourtia inermis fruits: characterization of malic acid as an inhibitor of the enzymes

et al. 2015

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Flacourtia inermis Roxb. (Flacourtiaceae), is a moderate sized tree cultivated in Sri Lanka for its fruits known as Lovi. The current study was undertaken to study the biological activity of extracts of the fruits in an attempt to increase the value of the under exploited fruit crops. Fruits of F. inermis were found to be rich in phenolics and anthocyanins. Polyphenol content of the fruits was determined to be 1.28 g gallic acid equivalents per 100 g of fresh fruit and anthocyanin content was estimated as 108 mg cyanidin-3-glucoside equivalents per 100 g of fresh fruits. The EtOAc extract showed moderate antioxidant activity in the DPPH radical scavenging assay with IC 50 value of 66.2 ppm. The EtOAc and MeOH extracts of the fruits also exhibited inhibitory activities toward α-glucosidase, α-amylase and lipase enzymes with IC 50 values ranging from 549 to 710 ppm, 1021 to 1949 ppm and 1290 to 2096 ppm, respectively. The active principle for the enzyme inhibition was isolated through activity-guided fractionation and was characterized as (S)-malic acid. The results of this study indicate that F. inermis fruits have the potential to be used in health foods and in nutritional supplements.

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Section: Resultsmentioning

confidence: 99%

Antioxidant property and α $$ \boldsymbol{\upalpha} $$ -glucosidase, α $$ \boldsymbol{\upalpha} $$ -amylase and lipase inhibiting activities of Flacourtia inermis fruits: characterization of malic acid as an inhibitor of the enzymes

et al. 2015

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“…The ␣-hydroxycarbonyl functional unit is ubiquitous in natural products and bioactive compounds, such as, e.g., carbohydrates, antibiotics, and antitumor agents; therefore, it is also present in synthetic intermediates and in chiral auxiliaries in view of the stereodirecting ability of the hydroxy group (8). The ␣-functionalization of carbonyl compounds most often relies on the reaction of enolate anions, or enol derivatives with electrophiles.…”

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confidence: 99%

Expanding the scope of asymmetric electrophilic atom-transfer reactions: Titanium- and ruthenium-catalyzed hydroxylation of β-ketoesters

Toullec

Bonaccorsi

Mezzetti

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

129

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The enantioselective formation of a quaternary stereogenic center coinciding with a hydroxylation process is a very rare reaction from a homogeneous catalysis point of view. Indeed, to our knowledge, no asymmetric transition-metal-catalyzed direct hydroxylation has been reported before. We describe here our initial study concerning the enantioselective ␣-hydroxylation of various ␤-ketoesters catalyzed by Lewis-acidic complexes. Specifically, it was found that the Ti complex [TiCl2((R,R)-1-Np-TADDOLato)(MeCN)2] affords the hydroxylated products in high yield and enantioselectivities up to 94% enantiomeric excess when using 2-(phenylsulphonyl)-3-(4-nitrophenyl)oxaziridine as the oxidizing agent. Chiral enantiopure compounds of the latter type have been used previously in stoichiometric asymmetric hydroxylation reactions. We also show that, in a complementary approach with H2O2 as the oxidant, the Ru(II) complex [RuCl(OE 2)((S,S)-PNNP)]PF6 catalyzes the same type of transformation in a case of substrates showing a very substantial extent of enolization under reaction conditions; being, however, unreactive toward only weakly enolized ␤-ketoesters.R eactions involving both the formation of new carbonheteroatom bonds and the concomitant generation of a new stereogenic center are prototypical transformations in asymmetric catalysis. Thus, for example, hydroboration, hydrosilylation, epoxidation, and aziridination of olefins, as well as allylic substitutions with heteroatom nucleophiles, have been extensively studied (1). However, catalytic halogenations, in particular fluorinations, and direct hydroxylations have received much less attention in the asymmetric catalysis community.Recently, we developed an enantioselective catalytic process in which ␤-ketoesters are fluorinated at the 2-position with an electrophilic fluorine donor such as Selectfluor [also called F-TEDA (TEDA, triethylenediamine), 1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis{tetrafluoroborate}] in the presence of a Lewis-acidic chiral titanium catalyst (1, Scheme 1, Fig. 1 (2-5). Our work inspired further developments involving chiral Pd catalysts (6) and chiral phase transfer catalysts for the same type of fluorination (7).The ␣-hydroxycarbonyl functional unit is ubiquitous in natural products and bioactive compounds, such as, e.g., carbohydrates, antibiotics, and antitumor agents; therefore, it is also present in synthetic intermediates and in chiral auxiliaries in view of the stereodirecting ability of the hydroxy group (8). The ␣-functionalization of carbonyl compounds most often relies on the reaction of enolate anions, or enol derivatives with electrophiles. The direct activation of the enol form of keto derivatives has recently been introduced as a new synthetic methodology to achieve ␣-amination (9) or, as already mentioned, ␣-halogenation (2-5). So far, the only straightforward enantioselective ␣-hydroxylation is the reaction of enolate salts with enantiopure N-sulfonyloxaziridines, acting as electrophilic oxygen sources, as dev...

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“…1 Among the few reported synthetic strategies for introducing this moiety, the benzoin reaction remains perhaps, the most direct. [2][3][4][5][6] The benzoin condensation reaction, one of the oldest C-C bond forming reactions in organic chemistry, has been developed for self-condensation of aromatic aldehydes into α-hydroxy carbonyl compounds using toxic cyanide ion in basic media.…”

Section: Introductionmentioning

confidence: 99%

Polymer Supported Cyanide as an Efficient Catalyst in Benzoin Condensation: An Efficient Route to α-Hydroxy Carbonyl Compounds

Kiasat

Badri²,

Sayyahi³

2009

Bulletin of the Korean Chemical Society

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α‐Hydroxy Acids in Enantioselective Syntheses

Cited by 332 publications

References 0 publications

Antioxidant property and α $$ \boldsymbol{\upalpha} $$ -glucosidase, α $$ \boldsymbol{\upalpha} $$ -amylase and lipase inhibiting activities of Flacourtia inermis fruits: characterization of malic acid as an inhibitor of the enzymes

Antioxidant property and α $$ \boldsymbol{\upalpha} $$ -glucosidase, α $$ \boldsymbol{\upalpha} $$ -amylase and lipase inhibiting activities of Flacourtia inermis fruits: characterization of malic acid as an inhibitor of the enzymes

Expanding the scope of asymmetric electrophilic atom-transfer reactions: Titanium- and ruthenium-catalyzed hydroxylation of β-ketoesters

Polymer Supported Cyanide as an Efficient Catalyst in Benzoin Condensation: An Efficient Route to α-Hydroxy Carbonyl Compounds

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