Antonio Hidalgo Navarro

A new and expeditious strategy for the synthesis of β-amino acids from Δ2-oxazolines

Abstract A new, mild two-step synthesis of racemic β-amino acids starting from 2-alkyl-Δ2-oxazolines is described. The process implies the initial formation of masked N-substituted or N-unsubstituted β-enamino acid derivatives followed by chemoselective reduction of the enamino moiety. The process takes place with high yields, total chemoselectivity and moderate diastereoselectivity.

Synthesis and C-alkylation of C-protected β-enamino acid derivatives from oxa- thia- and imidazolines

Abstract Various heterocycles 3a-h can be readily metallated and condensed with a variety of organic nitriles to afford C-protected β-enamino acid derivatives 1 (or 2). Procedures for alkylation of compounds 1 to obtain 2 as well as a “one-pot” preparation of 2 from 3 are also described.

Modeling for the active site nitrate reductase. Oxidation of the complex [MovO(O2CC(S) CH3Ph)2]− by nitrate and nitrite in methanol

Abstract Under acid conditions the [MoVIO2(O2CC(S)CH1Ph)2]2 reacts with thiols to yield the monomeric [MoVO(O2CC(S)CH3Ph)2] and disulfide. The reduced complex [MoVO(O2CC(S)CH3Ph)2]− can react with NO3− and NO2− in a one-electron step yeilding respectively NO2 and NO and the original molybdenum (VI)-dioxo complex. The experimental pseudo-first-order rate constant with respect to the Mo(V) complex at 25°C was found to be kobs=2.3×10−4s−1 for NO3− and kobs=1.0×10−2 for NO2−. Oxo transfers to and from the substrate have been coupled to produce a catalytic system which turns over the reaction RSH+(No3− or NO2−)+H+a 1 2 [ RS ] 2 +( NO ] 2 or NO )+ H 2 O , in which thiols, NO1− and NO2− serve as a model substrates and molybdenum complex as a catalyst. This result has permitted us to consider the system as a possible model for the nitrate reductase ‘Chlorella’ (S.P. Cramer et al., J. Am. Chem. Soc., 106 (1984) 1467; G.N. Geoige et al., Biochem. J., 259 (1989) 693).

A new and general synthesis of N-substituted fluorinated β-iminosulfoxides

Abstract Reaction of fluorinated imidoyl chlorides 1 with lithium enolates of chiral non-racemic methyl p -tolyl sulfoxide or racemic methyl phenyl sulfoxide 2 gave N -substituted γ-fluorinated β-iminosulfoxides 3 in excellent yields as the major tautomer with Z geometry.

A new and mild synthesis of β-amino acids from masked β-enamino acid derivatives

A new method of synthesis of racemic β-amino acids 6 by reduction of masked N-substituted and N-unsubstituted β-enamino acid derivatives 4 via C-protected β-amino acids 5 is described. The process occurs with high yields, total chemoselectivity and moderate diastereoselectivity. Readily available starting materials, inexpensive reagents and mild conditions are used to furnish derivatives 5 and 6.