Reaktionen von Oxazolin‐5‐on‐Anionen, VIII. α‐Substituierte α‐Aminosauren durch Alkylierung von Oxazolin‐5‐onen

Abstract

Alkylation of oxazolin-5-ones 1 with alkyl halides/ethyldiisopropylamine in dipolar aprotic solvents yields 4,4-disubstituted oxazolin-5-ones 2, which are cleaved with HCl/acetic acid to give a-amino acids 3. The introduction of cycloheptatrienyl residues with tropylium perchlorate/triethylamine in benzene is described. Oxazolin-5-ones may be considered as nucleophilic acyl equivalents. This is demonstrated by alkylation of 4-isopropyl-2-phenyl-2-oxazolin-5-one (1 b) to give 4-isopropyl-4-(2-nitrobenzyl)-2-phenyl-2-oxazolin-5-one (20 which may be transformed into isopropyl 2-nitrobenzyl ketone (12). Zur Einfuhrung einer Verzweigung in a-

Direct Asymmetric α‐Sulfamidation of α‐Branched Aldehydes: A Novel Approach to Enamine Catalysis

“…Related methods for the alkylation of modified naturally occurring amino acids with self-reproduction of the stereocentre have been developed: for imidazolidinones [17] and oxazolidinones [18] (Seebach [19] ), or oxazaborolidinones [20] and openchained borane-aminoester adducts. [21] Deprotonated oxazolin-5-ones (azlactones) have for some time been used as amino acid enolate equivalents in the synthesis of racemic α-alkylated amino acids, [22,23] often followed by separation of diastereomeric dipeptides. [23] More recent developments have also seen the emergence of asymmetric catalytic variants, [24,25] of which the palladium-catalysed approach devised by Trost et al has been successfully utilised for the total synthesis of sphingofungin F.…”

“…13 C NMR (100 MHz, CDCl 3 ): δ = 7.6 (+), 13.8 (+), 22.6 (-), 25.4 (-), 26.9 (-), 33.3 (-), 71.0 (q), 125.6 (+), 129.9 (+), 133.2 (+), 133.6 (+), 136.6 (q), 147 …”

ChemInform Abstract: Peptides Containing Dialkylglycines. Part 3. The Alkylation of 2‐Trifluoromethyl‐4‐alkyloxazolin‐5(2H)‐ones, and Partition Studies on N‐Acetyl‐αα‐dialkylglycinamides.

“…spectra as 2-carbamoyl-2,4diisobutyl-imidazol-5-one [8] . Ammonolysis of the three 2,4,4-trisubstituted oxazolinones prepared proceeded as 23 1 examined the alkylation of 2-trifluoromethyl4alkyl-oxazolin-5(2H)-ones (Scheme 1, [2] -+ [3J, R' = CF,), which avoids the preparation of the free dialkylglycine. Ammonolysis of the three 2,4,4-trisubstituted oxazolinones prepared proceeded as 23 1 examined the alkylation of 2-trifluoromethyl4alkyl-oxazolin-5(2H)-ones (Scheme 1, [2] -+ [3J, R' = CF,), which avoids the preparation of the free dialkylglycine.…”

“…Steglich et al (2,3 ) showed recently that 2-phenyl-oxazolin-5(4H)-one [ 11 (R' = Ph) can be dialkylated to [3] (R' = Ph) in good yield under mild conditions using active alkyl halides and Hunig's base in dipolar aprotic solvents. * However, attempts by us to prepare 2-trifluoromethyl-oxazolin-5(4H)-one [ 11 (R' = CF3) from N-trifluoroacetylglycine proved unsuccessful.…”

“…* However, attempts by us to prepare 2-trifluoromethyl-oxazolin-5(4H)-one [ 11 (R' = CF3) from N-trifluoroacetylglycine proved unsuccessful. This failure to prepare [l] (R' =CF3) as a common substrate for substitution constrained us to the alkylation of individual 'pseudo-oxazolinones' of type [2] (R' = CF3), whose preparation has been well documented by Weygand et al ( 6 ) from protein amino acids. Treatment of either the acid chloride or the anhydride with triethylamine gave dark red viscous oils which showed no characteristic oxazolinone C=O stretching absorptions at 1800-1860 cm-' .…”