Refernces
10.1016/S0040-4020(00)01008-5
The research focuses on the synthesis of spiroazabicycloalkane amino acid scaffolds, which serve as reverse-turn inducer dipeptide mimics. These conformationally constrained molecules are designed to mimic Ala-Pro dipeptide units or more generally, the central (i+1 and i+2) residues of β-turns in peptide chains. The methodology involves a series of chemical reactions starting from known compounds, utilizing reagents such as LiEt3BH, Ac2O, allyltributyl tin, BF3.Et2O, OsCl3, and NaBH4, among others, to produce the desired scaffolds. The experiments include hydrogenolysis, hydrolysis, protection of nitrogen atoms, dihydroxylation, oxidation, and olefination steps. The analyses used to characterize the intermediates and final products encompass 'H and 13C NMR spectroscopy, elemental analysis, mass spectrometry, and optical rotation measurements. Single crystal diffraction analysis was also performed to secure the configuration of the diastereoisomeric alcohols. The study successfully demonstrates a practical approach to synthesize these constrained scaffolds, which could potentially improve peptide-receptor affinity by interacting with hydrophobic pockets, thereby enhancing the metabolic stability of peptides.
10.1021/ja992125d
The research focuses on the development of a new radical cascade methodology for synthesizing vicinal singly and doubly acylated oxime ethers, which are potential precursors for vicinal di- and tricarbonyl compounds. The purpose of this study was to overcome the challenges in synthesizing these compounds through the coupling of multiple radical one-carbon (C1) synthons, such as carbon monoxide (CO) and sulfonyl oxime ethers. The researchers successfully demonstrated that a three-component coupling reaction involving RX, CO, and phenylsulfonyl oxime ether B, mediated by allyltributyltin and initiated by AIBN, could yield R-acyl-substituted aldoximes with high efficiency. The study concluded that this new radical cascade strategy not only expands the scope of radical C1 chemistry but also offers a versatile synthetic methodology for incorporating multiple C1 units into important nitrogen-containing heterocycles. The chemicals used in the process include phenylsulfonyl oxime ether B, allyltributyltin, AIBN, alkyl iodides, and carbon monoxide, among others.
10.1016/j.tet.2006.03.032
The research focuses on the enantioselective allylation of aldehydes using chiral (salen)chromium(III) complexes as catalysts. The purpose of the study was to develop a novel and efficient method for the asymmetric allylation of aldehydes, a significant process in organic synthesis. The researchers investigated the reaction of allylstannanes with glyoxylates, glyoxals, and simple aromatic and aliphatic aldehydes, catalyzed by chiral (salen)Cr(III) complexes. They found that the reaction proceeded smoothly for reactive 2-oxoaldehydes and allyltributyltin in the presence of small amounts of (salen)Cr(III)BF4 under mild conditions. However, for other simple aldehydes, high-pressure conditions were required to obtain good yields. The classic chromium catalyst, easily prepared from commercially available chloride complex, afforded homoallylic alcohols usually in good yield and with enantiomeric purity of 50–79% ee. The study concluded that the developed method is reproducible, not very sensitive to external factors such as oxygen or moisture, and requires only 1–2 mol % of the catalyst. The chemicals used in the process included various metallosalen complexes, allyltributyltin, and different aldehydes such as n-butyl glyoxylate, iso-propyl glyoxylate, and tert-butyl glyoxylate, among others.
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