50622-10-1Relevant articles and documents
Synthesis of functionalised bicyclic α-methylene-γ-butyrolactones from 2,3-cyclohexene acetal via radical cyclisation approach
Vankar,Chaudhuri
, p. 885 - 899 (1991)
2,3-Cyclohexene acetal, wherein the acetal functionality is derived from 2R,3R(+)-tartaric acid, has been transformed regioselectively into functionalised bicyclic α-methylene-γ-butyrolactones via radical cyclisations. The radicals were derived from n-bu3-SnH reactions with secondary bromides and a tertiary nitro compound.
Left-Handed Helix of Three-Membered Ring Amino Acid Homopeptide Interrupted by an N-H···Ethereal O-Type Hydrogen Bond
Koba, Yurie,Ueda, Atsushi,Oba, Makoto,Doi, Mitsunobu,Kato, Takuma,Demizu, Yosuke,Tanaka, Masakazu
supporting information, p. 7830 - 7834 (2018/12/14)
A chiral three-membered ring Cα,α-disubstituted α-amino acid (R,R)-Ac3cdMOM, in which the α-carbon is not a chiral center, but two side chain β-carbons are chiral centers, was synthesized from dimethyl l-(+)-tartrate, and its homopeptides were prepared. X-ray crystallographic analysis of (R,R)-Ac3cdMOM pentapeptide showed bent left-handed (M) 310-helical structures with an unusual intramolecular hydrogen bond of the N-H···O (ethereal) type. The left-handedness of the bent helices was exclusively controlled by the side-chain β-carbon chiral centers.
Synthesis of l-threitol-based crown ethers and their application as enantioselective phase transfer catalyst in Michael additions
Rapi, Zsolt,Nemcsok, Tamás,Pálv?lgyi, ádám,Keglevich, Gy?rgy,Grün, Alajos,Bakó, Péter
, p. 257 - 272 (2017/05/29)
A few new l-threitol-based lariat ethers incorporating a monoaza-15-crown-5 unit were synthesized starting from diethyl l-tartrate. These macrocycles were used as phase transfer catalysts in asymmetric Michael addition reactions under mild conditions to afford the adducts in a few cases in good to excellent enantioselectivities. The addition of 2-nitropropane to trans-chalcone, and the reaction of diethyl acetamidomalonate with β-nitrostyrene resulted in the chiral Michael adducts in good enantioselectivities (90% and 95%, respectively). The substituents of chalcone had a significant impact on the yield and enantioselectivity in the reaction of diethyl acetoxymalonate. The highest enantiomeric excess (ee) values (99% ee) were measured in the case of 4-chloro- and 4-methoxychalcone. The phase transfer catalyzed cyclopropanation reaction of chalcone and benzylidene-malononitriles using diethyl bromomalonate as the nucleophile (MIRC reaction) was also developed. The corresponding chiral cyclopropane diesters were obtained in moderate to good (up to 99%) enantioselectivities in the presence of the threitol-based crown ethers.
Synthesis and biological evaluation of bis(methoxy-methyl)-7,8-dihydro-[1, 4]dioxino[2,3-g]quinazolines as EGFR tyrosine kinase inhibitors
Lee, Yong Sup,Seo, Seon Hee,Yang, Beom-Seok,Lee, Jae Yeol
, p. 502 - 505 (2007/10/03)
A series of 7,8-bis(methoxymethyl)-7,8-dihydro-[1,4]dioxino[2,3-g] quinazolines were prepared and evaluated for their inhibition of phosphorylation of the isolated epidermal growth factor receptor (EGFR) enzyme and for their growth inhibition of the A431 cell line. Among them, compound 3c having a 3-iodophenyl ring was most potent (IC50 = 1.66 nM) against the isolated EGFR enzyme and also showed meaningful potency (GI50 = 1.99 μM) against the A431 cell line, although less than PD153035 (GI50 = 1.03 μM). However, compound 3e as the exact rigidified analogue of Erlotinib (Tarceva) was inferior to the original compound when compared to its reported data.
Chiral C2-symmetric 2,3-disubstituted aziridine and 2,6-disubstituted piperidine as chiral ligands in the addition reaction of diethylzinc with arylaldehydes
Shi, Min,Jiang, Jian-Kang,Feng, Yan-Shu
, p. 4923 - 4933 (2007/10/03)
Chiral C2-symmetric 2,3-disubstituted aziridines and 2,6-disubstituted piperidines having a β-amino alcohol moiety have been successfully synthesized and their catalytic chiral induction properties have been examined in the asymmetric addition reactions of diethylzinc with arylaldehydes in hexane. When N-(2,2-diphenyl-2-hydroxyethyl)-(S,S)-2,3-bis(methoxymethyl)aziridine 11 was used as a catalytic chiral ligand, sec-alcohols having (S)-configuration formed in high yields of 86-92% but low enantiomeric excesses (ee's) of 11-13%. However, when N-(2,2-diphenyl-2-hydroxyethyl)-(R,R)-2,6-disubstituted piperidine derivatives 16 and 20 were used as the chiral ligands under the same reaction conditions, the ee's of the corresponding sec-alcohols were 20-30 and 5-6%, respectively, along with the inversion of absolute configuration. A plausible mechanism for this inversion is proposed.
Enolic ortho esters. VIII. Synthesis of (2S,3S)-2,3-bis(methoxymethyl)-1,4,6-trioxaspiro[4.5]dec-7-ene
Collins, David J.,Crosby, Ian T.
, p. 1025 - 1030 (2007/10/03)
Enolic ortho ester (2S,3S)-2,3-bis(methoxymethyl)-1,4,6-trioxaspiro[4.5]dec-7-ene (10b) was synthesized in 65% yield by cycloadditon of acrolein with the ketene acetal (4S,5S)-4,5-bis(methoxymethyl)-2methylidene-1,3-dioxolan (7), derived by potassium t-butoxide treatment of (4S,5S)-4,5-bis(methoxymethyl)-1,3-dioxolan (4). Lewis acid catalysed reaction (TiCl4, CH2Cl2, -78°) of the enolic ortho ester (10b) with the ketene silyl acetal 3-phenylmethyl-2-trimethylsilyloxy-4,5-dihydrofuran (15) afforded the formyl keto ester 3-[4′,5′-bis(methoxymethyl)-2′-(4″-oxobutyl)-1′, 3′-dioxolan-2′-yl]-3-phenylmethyl-4,5-dihydrofuran-2(3H)-one (16) (39%) with only poor diastereoselectivity. Attempts to make the bis(phenylmethyl) analogue (10a) of enolic ortho ester (10b) were thwarted by the finding that the required ketene acetal (9), analogous to (7), could not be generated by elimination from (4S,5S)-2-bromomethyl-4,5-bis(phenylmethyl)-1,3-dioxolan (6), or from the derived phenyl selenoxide (8), under a variety of conditions.
Preparation of Chiral 2-(2-Bromobenzyl)-1,3-dioxolanes and Their Addition to Acylimines
Wuensch, Bernhard,Nerdinger, Sven
, p. 711 - 718 (2007/10/03)
A series of enantiomerically pure 2-(2-bromobenzyl)-1,3-dioxolanes 10 has been prepared by transacetalization of the dimethyl acetal 8 or the enol ether 7 with enantiomerically pure C2 symmetric 1,2-diols. We investigated the ability of the chiral 1,3-dioxolane moiety to control the diastereoselectivity during the addition of the aryllithium intermediates 18 to the acylimines 17. Those reactive aryllithium species were generated by bromine/lithium exchange at the bromo acetals 10. In this series the best diastereoselectivity was obtained by addition of the aryllithium intermediate 18b to the acylimine 17a to yield the diastereomeric addition products 19c/ 20c in a ratio of 72:28. After separation, the main diastereomer 19c was cyclized to afford the dihydroisoquinoline (R)-21, which was then hydrogenated to give the NMDA antagonistic 1-phenyl-1,2,3,4-tetrahydroisoquinoline (R)-2. The chiral auxiliary, the diol 9b, cleaved during the cylization of 19c, could be recovered in 89% yield.
Asymmetric Synthesis Using Chiral Acetals: Highly Diastereoselective Nucleophilic Addition of Grignard Reagents to Chiral 1-Oxo-β-tetralone 1-Acetals
Fujioka, Hiromichi,Kondo, Hiroshi,Annoura, Hirokazu,Yamamoto, Hirofumi,Ko, Tomoko,et al.
, p. 1488 - 1492 (2007/10/02)
Nucleophilic addition of organometallic reagents (Grignard reagents and organolithium reagents) to two chiral 1-oxo-β-tetralone 1-acetals (1a,b) was studied.Extremely high stereoselectivity was achieved in the reactions of 1a and 1b with Grignard reagents
The solution structures of chiral Ti(4+) alkoxides
Potvin, Pierre G.,Gau, Robert,Kwong, Patrick C. C.,Bianchet, Stephen
, p. 1523 - 1537 (2007/10/02)
1,4-Di-O-methyl-threitol and 1,2,5,6-tetra-O-methyl-L-mannitol were prepared by new, more convenient, and higher yielding routes.These and 1,2;5,6-di-O-isopropylidene-D-mannitol formed 2:2 complexes with Ti(OiPr)4, but did not readily form 1:2 complexes in the presence of excess Ti(4+). (1)H and (13)C nuclear magnetic resonance spectra showed that the structures in solution of the 2:2 complexes were analogous to solid-state structures of tartaric acid derivatives , i.e., possessing bridging diolate oxygens.In contrast, R,R- and meso-diisopropyl tartrates,N,N'-dibenzyl tartramide, and N,N'-di(2-phenyl)ethyl tartramide behaved very differently.The tartramides formed mixtures of complexes that became dominated by 2:3 complexes in the presence of excess Ti(OiPr)4.Two tertiary tartramides failed to provide well-defined complexes.The R,R-tartrate formed a monocyclic (nonbridged) 2:2 complex, but an equilibrating mixture of 1:2 and 2:2 complexes with excess Ti(4+).The equilibrium shifted upon cooling toward a 1:2 complex possessing a bridging diolate oxygen, as did the meso 1:2 complex.Other temperature-dependent phenomena were also studied. Key words: titanium(IV), chiral alkoxides, solution structures, NMR, Sharpless catalysts.
Asymmetric Synthesis Using Chiral Acetals: Highly Diastereoselective Addition of Organocerium Reagents to Chiral α-Aldoxime-Ether Acetal
Fujioka, Hiromichi,Fuji, Masahiro,Okaichi, Yoshihiko,Yoshida, Takayuki,Annoura, Hirokazu,et al.
, p. 602 - 605 (2007/10/02)
Nucleophilic addition of organometallic reagents to the chiral α-aldoxime-ether acetal (1) was studied.Among the reagents, organocerium reagents showed higher reactivity and stereoselectivity, giving the N-oxygenated chiral amine derivatives (6Aa-c) in a highly diastereoselective manner, whereas Grignard and organolithium reagents afforded no 6.As an application of the reaction, the synthesis of (-)-N-acetylamphetamine (11) was achieved.
