- Stereospecific Synthesis of 3,4-Dihydro-2 H-naphtho-1,4-oxazin-2-ones by Unification of Benzoxepine-4-carboxylates with Chiral Amino Acid Ethyl Esters
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A novel and efficient stereocontrolled method has been developed for the preparation of chiral 3,4-dihydro-2H-naphtho[1,2-b][1,4]oxazin-2-ones by the reaction of benzoxepine-4-carboxylates with chiral amino acid ethyl esters for the first time. The chiral 3,4-dihydro-2H-naphtho-1,4-oxazinones have been achieved in one step by the formation of C-N, C-C, and C-O bonds.
- Bhimapaka, China Raju,Kasagani, Veera Prasad,Kurma, Siva Hariprasad
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supporting information
p. 2976 - 2983
(2020/03/23)
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- Friedel-Crafts alkylation of natural amino acid-derived pyrroles with CF3-substituted cyclic imines
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Natural amino acid-derived ethyl 2-(1-pyrrolyl)alkanoates react with 2-trifluoromethyl-1-azacycloalkenes selectivity at the β-position of the pyrrole moiety to afford ethyl 2-[3-(1-trifluoromethyl-2-azacycloalkyl)pyrrol-1- yl]alkanoates.
- Shmatova, Olga I.,Shevchenko, Nikolay E.,Balenkova, Elizabeth S.,R?schenthaler, Gerd-Volker,Nenajdenko, Valentine G.
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- Synthetic studies toward paraherquamides E and F and related 13C-labeled putative biosynthetic intermediates: stereocontrolled synthesis of the α-alkyl-β-methylproline ring system
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A substituted 2R-allyl-3S-methylproline ethyl ester suitable for elaboration to paraherquamides E, F and related 13C-labeled putative biosynthesis intermediates have been prepared efficiently in six steps and?24% overall yield. The key steps are a 5-exo-trig cyclization of a zinc enolate on an unactivated alkene and a stereocontrolled alkylation of the enolate formed from 3S-methyl-pyrrolidine-1,2R-dicarboxylic acid 1-tert-butyl ester 2-ethyl ester.
- Sommer, Konrad,Williams, Robert M.
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p. 7106 - 7111
(2008/12/20)
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- Synthesis of diketopiperazines containing prolinyl unit - Cyclo(L-prolinyl-L-leucine), cyclo(L-prolinyl-L-isoleucine) and cyclo(L-tryptophyl-L-proline)
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Diketopiperazines cyclo(L-prolinyl-L-isoleucine) 4a, cyclo(L-prolinyl-L-leucine) 4b and cyclo(L-tryptophyl-L-proline) 6 were prepared from their respective suitably protected amino acid derivatives by standard peptide chemistry. Cyclo(L-(4-hydroxyprolinyl)-L-phenylalanine) 3, 4a and cyclo(L-prolinyl-L-tyrosine) 5 were tested for their antibacterial activity.
- Jhaumeer-Laulloo,Khodabocus,Jugoo,Jheengut,Sobha
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p. 765 - 768
(2007/10/03)
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- Synthesis of tert-Leucine and Related Amino Acids
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The 2,5-dialkoxypyrazines 3a and b were prepared in three steps from methyl glycinate hydrochloride (1) in an overall yield of 18 and 63 percent.Upon the addition of lithium organyls to 3b and subsequent acid hydrolysis the ethyl glycinates rac-7 were obtained.Key Words: tert-Leucine / Amino acids / Glycine cation equivalents / Bislactim ether method
- Groth, Ulrich,Huhn, Thomas,Porsch, Bettina,Schmeck, Carsten,Schoellkopf, Ulrich
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p. 715 - 720
(2007/10/02)
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- Stereochemical Studies of Thermal Intermolecular and Intramolecular N-Sulfonylimine Ene Reactions
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N-Sulfonylimine 2 has been found to undergo highly stereoselective thermal ene reactions with cyclohexene and trans-2-butene.In the cyclohexene example, the exclusive product was unsaturated amino acid derivative 6, the product of an endo transition state.With trans-2-butene, a 9:1 mixture of 18:22 was obtained, with the endo product again predominating.Intramolecular ene processes have been effected with the N-sulfonylimines derived from glyoxylates 25c and 26c.In the former case, the sole ene product was γ-lactone 30 derived from exo addition.In the latter process, a 9:1 mixture of cis-(E)-lactone 32 and cis-(Z)-lactone 33 was produced.Lactone 32 results from endo ene transition state 35 and 33 results from endo transition state 36.All attempts to effect intermolecular ene reactions of N-benzoylimine 39 failed.In trying to perform an intramolecular N-acylimine ene reaction, only Diels-Alder adduct 45 was produced from precursor 42.
- Tschaen, David M.,Turos, Edward,Weinreb, Steven M.
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p. 5058 - 5064
(2007/10/02)
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- STEREOCHEMISTRY OF THE GLYOXYLATE N-SULFONYLIMINE ENE REACTION
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Ene reactions of sulfonylimine 1b with cyclohexene and trans-2-butene are highly stereoselective, affording products 4 and 10, respectively.
- Tshaen, David M.,Weinreb, Steven M.
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p. 3015 - 3018
(2007/10/02)
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The Hofmann-Loeffler-Freytag reaction, carried out by irradiation in sulphuric acid of N-chloro-l-amino-acids 3a-d, gives δ-chlorinated compounds which can be cyclized to l-prolines 4a-e. This convenient synthesis does not affect the asymmetric centres of
- Titouani, S.Lafquih,Lavergne,Viallefont,Jacquier
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p. 2961 - 2965
(2007/10/02)
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