- PROCESS FOR THE SYNTHESIS OF OLEFINICALLY UNSATURATED CARBOXYLIC ACID ESTERS
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Process for the synthesis of olefinically unsaturated carboxylic acid esters of the formula R1R2C=CR3(COOR4), in which R1 is an alkyl, aryl or heteroaryl group that may be substituted with one or more halogen atoms and/or C1-C3-alkyl groups, R2 is an alkyl, aryl or heteroaryl group that may be substituted with one or more halogen atoms and/or C1-C3-alkyl groups, or hydrogen, or R1 and R2 form together with the carbon atom connecting them a C4-C7-carbocyclus that may be substituted with one or more halogen atoms and/or C1-C3-alkyl groups, R3 is hydrogen or a C1-C5-alkyl group, and R4 is an alkyl or aryl group with up to 20 carbon atoms, by reacting in a first step a carbonyl compound of formula R1R2C=O with an orthoester of formula CH2R3C(OR4)3, and by dehydrating in a second step the obtained intermediate compound R1R2COH- CHR3(COOR4).
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Page/Page column 6-7
(2010/11/29)
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- Synthesis of [Hexafluorovalyl1,1′]gramicidin S
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[Hexafluorovalyl1,1′]gramicidin S (8), in which two valine residues in the natural gramicidin S were replaced by L-hexafluorovaline (Hfv) residues, was synthesized by the solid-phase-synthesis and cyclization-cleavage method on benzophenone oxime resin. Though the racemic hexafluorovaline derivative was employed for the peptide synthesis, the desired product was isolated in moderate yield, probably reflecting the stable cyclic structure of 8. CD and 1HNMR spectra indicated that the conformation of 8 is similar to that of gramicidin S. The two β-turn structure and antiparallel β-sheet structure with four intramolecular hydrogen bondings were maintained in spite of introducing the hexafluorovaline residues. The dye-release experiment from lecithin vesicle and antimacrobial activity assay also indicated that 8 showed membrane-disturbing activity like gramicidin S, although the activity of 8 was somewhat weaker than gramicidin S.
- Arai, Toru,Imachi, Takashi,Kato, Tamaki,Ogawa, H. Iyehara,Fujimoto, Tsutomu,Nishino, Norikazu
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p. 1383 - 1389
(2007/10/03)
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- Efforts in Synthesizing α,β-Unsaturated Trifluoromethyl-substituted Aldehydes
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Hexafluoroacetone reacts with ethynylmagnesium bromide to yield (CF3)2C(OH)-CCH (1).Bromine can be added to the triple bond affording the cis/trans-isomer 2.With PCl5 1 yields the allene (CF3)2C=C=CClH (3).The addition of a metalated Schiff base to hexafluoroacetone leads to 4a which on hydrolysis yields (CF3)2C(OH)-CH2-CHO (4b).The reaction of (EtO)2P(O)CH2-R (R = CHO, CO2Et) with hexafluoroacetone gives α,β-unsaturated aldehydes or esters 6. 1,1,1-Trifluoroacetone provides analogous reactions.
- Abele, Herbert,Haas, Alois,Lieb, Max
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p. 3502 - 3506
(2007/10/02)
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- Synthesis of Fluorine-Containing Peptides. Analogues of Angiotensin II Containing Hexafluorovaline.
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γ,γ,γ,γ',γ',γ'-Hexafluorovaline and derivatives have been prepared and incorporated into angiotensin II by fragment condensation and solid-phase peptide synthesis.Hexafluorovaline derivatives showed general resistance toward various enzymatic digestions and the tendency to racemize extensively upon carboxyl activation.When the angiotensin II analogues were assayed on rat uterus, 5>AII had 133percent activity, 5>AII was inactive, and 1,DL-Hfv8>AII was a potent inhibitor of angiotensin II in vitro and in vivo.
- Vine, William H.,Hsieh, Kun-hwa,Marshall, Garland R.
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p. 1043 - 1047
(2007/10/02)
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- Synthesis and Thermolysis of Highly Halogenated Δ1-Pyrazolines
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The pyrolysis of highly halogenated Δ1-pyrazolines gives, in addition to cyclopropanes, rearranged olefins.
- Huff, Roger K.,Savins, Eric G.
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p. 742 - 743
(2007/10/02)
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