Synthesis of hydrazine and azapeptide derivatives by alkylation of carbazates and semicarbazones

2012 ◽  
Vol 90 (11) ◽  
pp. 985-993 ◽  
Author(s):  
Yesica Garcia-Ramos ◽  
Caroline Proulx ◽  
William D. Lubell
Keyword(s):  
Butyl Ester ◽  
Protecting Groups ◽  
Tert Butyl

Hydrazine and azapeptide analogs were synthesized effectively by alkylation of alkylidene carbazates and semicarbazones. In comparisons of benzylidene, benzhydrylidene, and fluorenylidene tert-butyl carbazates in alkylations using bases of different pKb character, superior conversion was obtained using the fluorenone derivative. Mild alkylation conditions were found employing Et4NOH as base and used to convert fluorenylidene tert-butyl carbazate into 13 different protected hydrazines. Moreover, racemization was avoided during alkylation of fluorenylidene semicarbazide in the synthesis of aza-propargylglycinylphenylalanine tert-butyl ester, the protecting groups from which could be selectively removed.

Biodegradation of cyclic and substituted linear oligomers of poly(3-hydroxybutyrate)

1995 ◽  
Vol 41 (13) ◽  
pp. 180-186 ◽  
Author(s):  
Helmut Brandl ◽  
Brigitte Aeberli ◽  
Reinhard Bachofen ◽  
Ingrid Schwegler ◽  
Hans-Martin Müller ◽  
...  
Keyword(s):  
Methyl Esters ◽  
Butyl Ester ◽  
Ester Group ◽  
Terminal Group ◽  
Protecting Groups ◽  
Clear Zone ◽  
Tert Butyl ◽  
Hairpin Loops ◽  
End Groups ◽  
Fmoc Group

Cyclic oligo(3-hydroxybutyrate), oligo(3-HB), was synthesized and purified, resulting in oligolides that contained three to seven (R)-3-hydroxybutyrate units (triolides up to heptolides). In addition, linear 3-HB octamers obtained as either tert-butyl or methyl esters were substituted with different end groups at the hydroxy end. The hydroxy terminus was replaced by either a benzyloxy, trifluoroacetoxy, crotonyloxy, (S)-3-hydroxybutyryloxy, or fluorenylmethylcarbonyloxy (FMOC) group. P(3-HB) hairpin loops occurred on the surface of certain regions of the polymer, especially of lamellar crystallites. Cyclic 3-HB oligomers provide a model system for these loops. It is assumed that they provide attachment points for the depolymerizing enzymes. All of the (R)-oligolides tested were degraded except the (R)-triolide. Triolides were not degraded, suggesting that enzymatic attack was prevented presumably by steric hindrance on the rigid ring system. Unsubstituted linear octamers were degraded. Biodegradation was prevented when the hydroxy terminus was protected by the FMOC group, but was not dependent on a free hydroxy terminal group: all other protecting groups did not prevent degradation. Substitution of the carboxy end by a methyl or tert-butyl ester group did not influence biodegradation.Key words: poly(3-hydroxybutyrate), oligolides, biodegradation, clear zone test.

scholarly journals Selective tert-Butyl Ester Deprotection in the Presence of Acid Labile Protecting Groups with Use of ZnBr2.

ChemInform ◽  
2005 ◽  
Vol 36 (1) ◽  
Author(s):  
Ramesh Kaul ◽  
Yann Brouillette ◽  
Zohreh Sajjadi ◽  
Karl A. Hansford ◽  
William D. Lubell
Keyword(s):  
Butyl Ester ◽  
Protecting Groups ◽  
Tert Butyl ◽  
Acid Labile

Synthesis of Optically Active Hydroxyalkyl Cycloheptatrienes: A Key Step in the Total Synthesis of 6,11-Methylene-LXB4

Synlett ◽  
2020 ◽  
Vol 32 (01) ◽  
pp. 45-50
Author(s):  
Udo Nubbemeyer ◽  
Analuisa Nava ◽  
Lukas Trippe ◽  
Andrea Frank ◽  
Lars Andernach ◽  
...  
Keyword(s):  
Carboxylic Acid ◽  
Total Synthesis ◽  
Structure Elucidation ◽  
Butyl Ester ◽  
Optically Active ◽  
Chiral Hplc ◽  
Reaction Conditions ◽  
Acid Product ◽  
Tert Butyl ◽  
Nabh4 Reduction

AbstractStarting from methyl cycloheptatrienyl-1-carboxylate, 6-acylation was successfully achieved employing glutaryl chloride in the presence of AlCl3 under controlled reaction conditions to furnish keto carboxylic acid product. After protection of this keto carboxylic acid as tert-butyl ester, reagent-controlled enantioselective reductions delivered configuration-defined methyl-6-hydroxylalkyl cycloheptatriene-1-carboxylates with up to 80% ee. Whereas simple NaBH4 reduction of the keto carboxylic acid and subsequent lactonization afforded a methyl-6-tetrahydropyranonyl cycloheptatriene-1-carboxylate. Resolution using chiral HPLC delivered the product enantiomers with up to >99% ee Finally, ECD analyses enabled structure elucidation. The products are used as key intermediates in enantioselective 6,11-methylene-lipoxin B4 syntheses.

Facile synthesis of tert-butyl ester of N-protected amino acids with tert-butyl bromide

1993 ◽  
Vol 34 (46) ◽  
pp. 7409-7412 ◽  
Author(s):  
Pierre Chevallet ◽  
Patrick Garrouste ◽  
Barbara Malawska ◽  
Jean Martinez
Keyword(s):  
Amino Acids ◽  
Butyl Ester ◽  
Facile Synthesis ◽  
Butyl Bromide ◽  
Tert Butyl

scholarly journals Crystal structure of 2-(4-allyl-4-methyl-2-oxo-1,4-dihydro-2H-benzo[d]- [1,3]oxazin-6-yl)-5-cyano-pyrrole-1-carboxylic acid tert-butyl ester, C22H23N3O4

2014 ◽  
Vol 229 (2) ◽  
pp. 127-128 ◽  
Author(s):  
Chuanhong Zhang ◽  
Jianguo Lin ◽  
Gaochao Lv ◽  
Yang Cao ◽  
Shineng Luo
Keyword(s):  
Crystal Structure ◽  
Carboxylic Acid ◽  
Butyl Ester ◽  
Tert Butyl

Abstract C22H23N3O4, triclinic, P1¯ (no. 2), a = 6.992(3) Å, b = 8.159(4) Å, c = 18.778(8) Å, α = 92.118(7)°, β = 93.463(7)°, γ = 101.623(7)°, V = 1045.9 Å3, Z = 2, Rgt(F) = 0.0576, wRref(F2) = 0.1778, T = 296 K.

Bis(ether) derivatives of tetrakis(2-hydroxyphenyl)ethene — Direct synthesis of (E)- and (Z)-bis(2-hydroxyphenyl)-bis(2-methoxyphenyl)ethene via the McMurry olefination reaction

2006 ◽  
Vol 84 (10) ◽  
pp. 1250-1253 ◽  
Author(s):  
Mee-Kyung Chung ◽  
Paul Fancy ◽  
Jeffrey M Stryker
Keyword(s):  
Supramolecular Chemistry ◽  
Direct Synthesis ◽  
Protecting Groups ◽  
Tert Butyl ◽  
Orthogonal Protection ◽  
Protection Strategies ◽  
Titanium Trichloride ◽  
Sterically Hindered ◽  
Derivatives Of

The direct synthesis of sterically hindered, partially etherified derivatives of tetrakis(2-hydroxyphenyl)ethene is reported by using the McMurry reductive olefination reaction on a range of differentially substituted 2,2′-dialkoxy benzophenone substrates. Three orthogonal protection strategies are demonstrated, incorporating β-silylethyl, 3-butenyl, and tert-butyl protecting groups, respectively, into the starting benzophenones. The latter proved most efficient, with both the McMurry coupling and deprotection steps occurring concomitantly under the McMurry conditions to directly yield the desired bis(2-hydroxyphenyl)-bis(2-methoxyphenyl)ethene as a 1:1 mixture of E- and Z-diastereoisomers.Key words: preorganized polyaryloxide ligands, McMurry olefination, titanium trichloride, supramolecular chemistry, tetrakis(2-hydroxyphenyl)ethene, 2,2′-disubstituted benzophenone.

ChemInform Abstract: tert-Butyl Ester or Benzylamide of the Dipeptide Pro-Gly as Organocatalysts for the Asymmetric Aldol Reaction.

ChemInform ◽  
2015 ◽  
Vol 46 (24) ◽  
pp. no-no
Author(s):  
Ierasia Triandafillidi ◽  
Aikaterini Bisticha ◽  
Errika Voutyritsa ◽  
Gerasimia Galiatsatou ◽  
Christoforos G. Kokotos
Keyword(s):  
Aldol Reaction ◽  
Butyl Ester ◽  
Asymmetric Aldol ◽  
Tert Butyl ◽  
Asymmetric Aldol Reaction
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