DMAP structure

Ga—E monomers. The central structural parameters of Ga-containing monomers dmap—Ga(R2)E(Tms)2 (E = P 65, As 66, Sb 67), which are summarized in Table 16, are comparable to those of analogously substituted Al—E monomers. 

Further, Wasserman and coworkers developed a direct acylation of stabilized phosphonium ylides by carboxylic acids in presence of the EDCI/DMAP (way c). This last method allows the introduction of a-aminoacid structures into the resulting P-oxo phosphorus ylides [19-25],opening the way to the total synthesis of depsipeptide elastase inhibitors [22,24] or cyclic peptidic protease inhibitor EurystatinA [20]. 

Similar structural results are obtained if one donor is neutral (e.g. DMAP) and the other donor is anionic (Cl ) (structure 21). The adducts possess extremely soft potentials and in solution the P NMR shifts are strongly temperature dependent [59]. It confirms the assertion that the adducts are very labile. 

Initial studies on the reaction of dmap -> Al(Me2)Sb(SiMe3)2 63 with -Bu3A1 and -Bu3Ga resulted in the formation of the expected adducts dmap -> AlMe2Sb(SiMe3)2 M(f-Bu)3 (M = A1 82, Ga 83). Their solid state structures were determined by single crystal X-ray diffraction130 (Fig. 38). 

Importantly, TV-carbamoyl derivatives of primary amines obtained from photolabile benzoins exist in varying proportions as cyclic hydroxyoxazolidinone tautomers. Therefore, the preparation of TV-carbamoyl derivatives of benzoins is applicable only for secondary amines and TV-alkylated amino acids. 244 At basic pH unsymmetrical benzoins, such as 3,5-dimethoxybenzoin, their mixed carbonate and carbamate derivatives, tend to equilibrate to the isomeric forms. Nevertheless, in TFA and aqueous solutions at pH 8 the structural integrity is fully maintained. 244 Preparation of 3,5-dimethoxybenzoin-derived carbamates of secondary amines and amino acids can be mediated by either CDI/methyl triflate in ni-tromethane 246 or 4-nitrophenyl chloroformate/DMAP in dry THF. 244 ... 

Abbreviations DCM, dichloromethane DIC, 1,3-diisopropylcarbodiimide DIEA, diiso-propylethylamine DMAP, 4-dimethylaminopyridine DMF, IVJV-dimethylformamide ELSD, evaporative light scattering detection HOBt, hydroxybenzotriazole IR, infrared LC/MS, high-pressure liquid chromatography/mass spectrometry NMM, V-methylmorpho-line NMR, nuclear magnetic resonance PyBop, benzotriazol-l-yloxytripyrrolidino-phosphonium hexafluorophosphate SAR, structure-activity relationship TFP, tetrafluorophenol THF, tetrahydrofuran. 

Construction of quaternary stereocenters by enantiocontrolled oxygen to carbon acyl shift is not limited to the azlactone structure. Using the pentaphenylated planar chiral DMAP derivative 79c (Scheme 13.42) Fu and Hills achieved rearrangement of O-acylated oxindoles 84 (Scheme 13.45) and benzofuranones 85 (Scheme 13.46) with very good yields and enantiomeric excesses up to 99% [88]. 

Phenyl chlorothionoformate (4.66 g, 27 mM) is added to a mixture of 2-chloro-(3, 5 -0-tetraisopropyldisiloxyl)adenosine (14 g, 25.8 mM), 4-dimethylaminopyridine (DMAP) (6.88 g, 56.4 mM) and acetonitrile (400 mL) at room temperature under nitrogen, and stirred overnight. The solvent is removed in vacuo and the residue is purified by column chromatography on silica gel (200 g) with ethyl acetate/hexane (4 6) to yield the title compound as a pale yellow powder (9.8 g, 56%, MP 153-155°C). NMR, IR and elemental analysis are confirmed the structure of the title compound. 

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