116838-41-6Relevant articles and documents
Conformational Behavior of Methyl (3R)-3-oxy>butanoate in Solutions: Effect of Intramolecular Hydrogen Bond
Li, Jun,Uzawa, Jun,Doi, Yoshiharu
, p. 1887 - 1894 (1997)
Methyl (3R)-3-oxy>butanoate (MHBOB) has been prepared as a model compound of the hydroxy terminal part of poly ; the NMR assignments and conformational analyses of the compound are reported.The NMR assignments of MHBOB were made by means of two-dimensional pulsed field gradient 1H-1H COSY and 1H-13C HMBC (heteronuclear multiple-bond correlation) spectroscopy.The conformational behavior of MHBOB generated by rotation about two CH2-CH bonds was investigated in chloroform and in aqueous solution at various temperatures by analysis of vicinal coupling in the 500-MHz 1H NMR spectra.In both chloroform and aqueous solution, the monomer unit adjacent to the methoxy group was found to adopt a similar conformational distribution to that of the P(3-HB) polymer backbone, in which the trans and gauche conformers were predominant, while the another gauche conformer was suppressed to almost zero.On the other hand, the monomer unit adjacent to the hydroxy group had a different conformational distribution relative to that of the other monomer unit, due to the formation of an intramolecular hydrogen bond between hydroxy and carbonyl groups.In chloroform, only the gauche conformer was predominant at temperatures between -60 and 57 deg C, and even the fraction of another gauche conformer was higher than that of trans conformer at low temperatures below 0 deg C.In aqueous solution, the fraction of gauche conformer was also higher than that of trans conformer, suggesting the formation of the intramolecular hydrogen bond.However, the formation of the intramolecular hydrogen bond in aqueous solution was not so strong as that in chloroform.
Total Synthesis of Pseudomonas aeruginosa 1244 Pilin Glycan via de Novo Synthesis of Pseudaminic Acid
Liu, Han,Zhang, Yanfeng,Wei, Ruohan,Andolina, Gloria,Li, Xuechen
, p. 13420 - 13428 (2017/10/05)
Pseudaminic acid (Pse) is a nonulosonic acid unique to bacterial species, found as a component of important cell surface glycans and glycoproteins in various pathogenic species, such as the critical hospital threat Pseudomonas aeruginosa. Herein we present the development of a facile and scalable de novo synthesis of Pse and its functionalized derivatives from easily available Cbz-l-allo-threonine methyl ester (16 steps in 11% yield). The key reactions in our de novo synthesis involve the diastereoselective glycine thioester isonitrile-based aldol-type reaction to create the 1,3-anti-diamino skeleton, followed by the Fukuyama reduction and the indium-mediated Barbier-type allylation. Moreover, we have studied the glycosylation of the Pse glycosyl donors and identified the structural determinants for its glycosylation diastereoselectivity, which enabled us to complete the total synthesis of P. aeruginosa 1244 pilin trisaccharide α-5NβOHC47NFmPse-(2→4)-β-Xyl-(1→3)-FucNAc.
Sensing remote chirality: Stereochemical determination of β-, γ-, and δ-chiral carboxylic acids
Tanasova, Marina,Anyika, Mercy,Borhan, Babak
supporting information, p. 4274 - 4278 (2015/04/14)
Determining the absolute stereochemisty of small molecules bearing remote nonfunctionalizable stereocenters is a challenging task. Presented is a solution in which appropriately substituted bis(porphyrin) tweezers are used. Complexation of a suitably derivatized β-, γ-, or δ-chiral carboxylic acid to the tweezer induces a predictable helicity of the bis(porphyrin), which is detected as a bisignate Cotton Effect (ECCD). The sign of the ECCD curve is correlated with the absolute stereochemistry of the substrate based on the derived working mnemonics in a predictable manner.
