- Enantioselective Synthesis of β-Amino Acid Derivatives Enabled by Ligand-Controlled Reversal of Hydrocupration Regiochemistry
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A Cu-catalyzed enantioselective hydroamination of α,β-unsaturated carbonyl compounds for the synthesis of β-amino acid derivatives was achieved through ligand-controlled reversal of the hydrocupration regioselectivity. While the hydrocupration of α,β-unsaturated carbonyl compounds to form α-cuprated species has been extensively investigated, we report herein that, in the presence of an appropriate ancillary chiral ligand, the opposite regiochemistry can be observed for cinnamic acid derivatives, leading to the delivery of the copper to the β-position. This copper can react with an electrophilic aminating reagent, 1,2-benzisoxazole, to provide enantioenriched β-amino acid derivatives, which are important building blocks for the synthesis of natural products and bioactive small molecules.
- Buchwald, Stephen L.,Guo, Sheng,Zhu, Jiaqi
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supporting information
p. 20841 - 20845
(2020/09/16)
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- Immobilization of cis-4-Hydroxydiphenylprolinol Silyl Ethers onto Polystyrene. Application in the Catalytic Enantioselective Synthesis of 5-Hydroxyisoxazolidines in Batch and Flow
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A new family of polystyrene-supported cis-4-hydroxydiphenylprolinol silyl ethers has been prepared, and the resulting polymers have been evaluated as organocatalysts to promote the tandem reaction between N-protected hydroxylamines and α,β-unsaturated aldehydes in batch and flow. The new PS-supported catalysts compare favorably with well-established immobilized J?rgensen-Hayashi catalysts, affording 5-hydroxyisoxazolidines as single diastereoisomers with high enantioselectivities and good yields (up to 83% yield, up to 99% ee). (Figure presented.).
- Lai, Junshan,Sayalero, Sonia,Ferrali, Alessandro,Osorio-Planes, Laura,Bravo, Fernando,Rodríguez-Escrich, Carles,Pericàs, Miquel A.
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p. 2914 - 2924
(2018/08/17)
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- SmI2-promoted imino-Reformatsky reaction for facile synthesis of enantioenriched β-amino acid esters
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A facile and efficient method for the stereoselective synthesis of β-amino acid esters via SmI2-promoted imino-Reformatsky reaction is described. Asymmetric addition of tert-butyl bromoacetate to N-tert-butanesulfinyl aldimines afforded β-amino
- Wang, Li,Shen, Chun,Xu, Ming-Hua
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experimental part
p. 61 - 65
(2011/12/15)
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- Organocatalytic asymmetric mannich reactions with JV-Boc and JV-Cbz protected α-amido sulfones (Boc: Tert-butoxycarbonyl, Cbz: Benzyloxycarbonyl)
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Different malonates and βketoesters can react with N-tert-butoxycarbonyl- (N-Boc) and N-benzyloxycarbonyl- (N-Cbz) protected α-amido sulfones in an organocatalytic asymmetric Mannich-type reaction. The reaction makes use of a simple and easily obtained ph
- Marianacci, Olindo,Micheletti, Gabriele,Bernardi, Luca,Fini, Francesco,Fochi, Mariafrancesca,Pettersen, Daniel,Sgarzani, Valentina,Ricci, Alfredo
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p. 8338 - 8351
(2008/04/01)
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- A new route to enantiopure β-aryl-substituted β-amino acids and 4-aryl-substituted β-lactams through lipase-catalyzed enantioselective ring cleavage of β-lactams
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A simple and efficient direct enzymatic method was developed for the synthesis of 4-aryl-substituted β-lactams and the corresponding β-amino acid enantiomers through the CAL-B (lipase B from Candida antarctica)-catalyzed enantioselective (E > 200) ring cleavage of the corresponding racemic β-lactams with 1 equiv. of H2O in i-Pr2O at 60°C. The product (R)-β-amino acids (ee ≥ 98%, yields ≥ 42%) and unreacted (S)-β-lactams (ee ≥ 95%, yields ≥ 41%) could be easily separated. The ring opening of enantiomeric β-lactams with 18% HCl afforded the corresponding enantiopure β-amino acid hydrochlorides (ee ≥ 99%).
- Forro, Eniko,Paal, Tihamer,Tasnadi, Gabor,Fueloep, Ferenc
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p. 917 - 923
(2007/10/03)
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- Highly diastereoselective and enantioselective preparation of homoallylic amines: Application for the synthesis of β-amino acids and γ-lactams
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Reactions of N-silyl- and N-aluminoimines with B- allyldiisopinocampheylborane in the presence of methanol, followed by oxidative workup furnished homoallylic amines in good yields and high ee. A 11B NMR spectroscopy study revealed that the reactions do not proceed, even at room temperature, unless a molar equivalent of water or methanol is added. The first reagent-controlled asymmetric crotylboration and alkoxyallylboration of aldimines furnishing β-methyl or βalkoxy homoallylic amines in very high diastereoselectivity and enantioselectivity are reported herein. Crotylboration and alkoxyallylboration of imines proceed only with the "allyl"-boron "ate" complexes, instead of the "allyl"-dialkylboron reagents used with aldehydes. The addition of methanol is necessary for these reactions as well. Application of this methodology for the conversion of representative nitriles to β-amino acids in two steps has been described. Additionally, a procedure for the preparation of chiral δ-amino alcohols and γ-lactams from nitriles is also reported.
- Ramachandran, P. Veeraraghavan,Burghardt, Thomas E.
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p. 4387 - 4395
(2007/10/03)
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- Synthesis of the Alkaloid Homaline in (+/-) and Natural (S,S)-(-) Forms, using Amination and Transamidative Ring Expansion in Liquid Ammonia
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Synthesis of the alkaloid homaline in (+/-) and natural (S,S)-(-) forms is reported.Linking of 2-azacyclooctanone units either directly or successively using 1,4-dihalogenobutanes or 1,4-dihalogenobut-2-ynes is examined. (+/-)-5-Methyl-4-phenyl-1,5-diazacyclooctan-2-one is first made by a 2,2'-dithiodipyridine/triphenylphosphine-mediated cyclisation, and then by amination and transamidative ring expansion from N-(3-chloropropyl)-4-phenylazetidin-2-one in liquid ammonia, followed by N-methylation.Coupling through a 1,4-dihalogenobutane of either the N-methylated azalactam, or the unmethylated azalactam followed by methylation, gave homaline in (+/-) and meso forms. (R)-(-)-Phenylglycine was converted via (S)-β-phenyl-β-alanine into an (S)-β-lactam which was then alkylated with 1-bromo-3-chloropropane, and aminated and ring expanded in liquid ammonia.Coupling of the homochiral azalactam (2 mol) so formed with 1,4-dibromobutane, followed by N-methylation, gave (S,S)-(-)-homaline identical with the natural material.
- Crombie, Leslie,Haigh, David,Jones, Raymond C. F.,Mat-Zin, Ab. Rasid
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p. 2047 - 2054
(2007/10/02)
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- Carbohydrates as Chiral Templates: Diastereoselective Synthesis of N-Glycosyl-N-homoallylamines and and β-Amino Acids from Imines
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Complexing properties and chirality of carbohydrates were utilized in diastereoselective reactions of O-pivaloylated N-galactosylimines with allylsilanes and -stannanes.With allyltrimethylsilane in the presence of SnCl4 imines 2 of aromatic and heteroaromatic aldehydes were converted to homoallylamines 3, giving ratios of diastereomers higher than 7:1.No addition products derived from α-anomeric aromatic imines were formed.Aliphatic homoallylamines 3 were synthesized by using allyltributylatannane in the presence of SnCl4.Both α- and β-anomeric aliphatic imines reacted with the allylstannane.They gave the same ratio of diastereomers and showed the same sense of asymmetric induction.
- Laschat, Sabine,Kunz, Horst
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p. 5883 - 5889
(2007/10/02)
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- THE USE OF β-LACTAMS IN THE SYNTHESIS OF SPERMINE AND SPERMIDINE ALKALOIDS. TOTAL SYNTHESIS OF HOMALINE
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The optically active plant product homaline (6) has been synthesized in a convergent sequence starting with β-phenyl-β-alanine and putrescine (14).The key transformation in this sequence is the ring expansion by transamidation of a functionalized chiral β-lactam precursor.
- Wasserman, Harry H.,Berger, Gregory D.
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p. 2459 - 2464
(2007/10/02)
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- Analogues of 2'(3')-O-L-phenylalanyladenosine as substrates and inhibitors of ribosomal peptidyltransferase
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The chemical syntheses of 2'(3')-O-(L-3-amino-3-phenylpropionyl)adenosine (2e), the corresponding D stereoisomer 2f, 2'(3')-O-(DL-phenylglycyl)adenosine (2g), 2'(3')-O-(N-benzylglycyl)adenosine (2h), and 9-(2-O-L-phenylalanyl-β-D-xylofuranosyl)adenine (3b) are described. Compounds 2e-h were obtained by acylation of 5'-O(4-methoxytrityl)adenosine with the appropriate N-benzyloxycarbonyl or N-tert-butoxycarbonyl amino acids with dicyclohexylcarbodiimide in pyridine. The corresponding reaction of N-(benzyloxycarbonyl)-D-phenylglycine led to an almost complete racemization of the aminoacyl residue (compounds 2c and 2g). Subsequent chromatographic separation and deprotection of intermediates 2a-d afforded the desired target derivatives 2e-h. Product 3b was obtained by a similar acylation of 9-(3,5-O-isopropylidene-β-D-xylofuranosyl)adenine with N-(benzyloxycarbonyl)-L-phenylalanine, followed by deblocking. The NMR spectra of 2' and 3' isomers of stereoisomers 2a and 2b are discussed. Compounds 2g and 3b are both substrates and inhibitors of Escherichia coli ribosomal peptidyltransferase, although the activity of 3b is low. Derivatives 2e,f,h do not accept AcPhe from N-AcPhe-tRNA in a peptidyltransferase-catalyzed reaction, but they inhibit the puromycin reaction in the same system. The order of inhibitory activity is 2e>2f>2h. The implications of these findings for the mechanism of peptidyltransferase and comparison of the latter with the action of chymotrypsin are discussed.
- Zemlicka,Bhuta,Bhuta
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p. 167 - 174
(2007/10/02)
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