60434-72-2Relevant academic research and scientific papers
The entrapment of chiral guests with gated baskets: Can a kinetic discrimination of enantiomers be governed through gating-
Wang, Bao-Yu,Stojanovic, Sandra,Turner, Daniel A.,Young, Tanya L.,Hadad, Christopher M.,Badjic, Jovica D.
, p. 4767 - 4775 (2013)
The capacity of gated hosts for controlling a kinetic discrimination between stereoisomers is yet to be understood. To conduct corresponding studies, however, one needs to develop chiral, but modular and gated hosts. Accordingly, we used computational (RI-BP86/TZVP//RI-BP86/SV(P)) and experimental (NMR/CD/UV/Vis spectroscopy) methods to examine the transfer of chirality in gated baskets. We found that placing stereocenters of the same kind at the rim (R1=CH3, so-called bottom) and/or top amide positions (R2=sec-butyl) would direct the helical arrangement of the gates into a P or M propeller-like orientation. With the assistance of 1H NMR spectroscopy, we quantified the intrinsic (thermodynamic) and constrictive (kinetic) binding affinities of (R)- and (S)-1,2-dibromopropane 5 toward baskets (S3b/P)-2, (S3t/M)-3, and (S3bt/P)-4. Interestingly, each basket has a low (≤1.3 kcal mol-1), but comparable (de3b/P)-2, with a set of S stereocenters at the bottom and P arrangement of the gates, would capture (R)-5 at a faster rate (kinR/kinS=2.0±0.2). Basket (S3t/M)-3, with a set of S centers at the top and M arrangement of the gates, however, trapped (S)-5 at a faster rate (kin R/kinS=0.30±0.05). In light of these findings, basket (S3bt/P)-4, with a set of S stereocenters installed at both top and bottom sites along with a P disposition of the gates, was found to have a lower ability to differentiate between enantiomeric (R/S)-5 (k inR/kinS=0.8). Evidently, the two sets of stereocenters in this "hybrid" host acted concurrently, each with the opposite effect on the entrapment kinetics. Gated baskets are hereby established to be a prototype for quantifying the kinetic discrimination of enantiomers through gating and elucidating the electronic/steric effects on the process. Falling into a trap: Controlling the rate at which two stereoisomeric compounds enter a host presents a challenge. Gated molecular baskets (see figure) are shown to be excellent prototypes for implementing a kinetic differentiation of guests. Copyright
Ethylene Biosynthesis. 6. Synthesis and Evaluation of Methylaminocyclopropanecarboxylic Acid
Pirrung, Michael C.,McGeehan, Gerard M.
, p. 2103 - 2106 (1986)
The compound (1R,2S)-2-methyl-1-aminocyclopropanecarboxylic acid (MeACC) has been synthesized in racemic and optically active forms.It has been studied as a substrate and inhibitor for ethylene biosynthesis in mung bean hypocotyls.Both KI and Km for MeACC are the same and identical with Km for ACC, strongly implying that they compete for the same site.MeACC is converted to propene by mung bean hypocotyls.
Stereochemical control in microbial reduction. 12. (S)-4-nitro-2-butanol as a source to synthesize natural products
Nakamura,Kitayama,Inoue,Ohno
, p. 91 - 96 (2007/10/02)
(S)-(+)-4-Nitro-2-butanol (1) obtained by the stereoselective reduction of 4-nitro-2-butanone by bakers' yeast was employed for the syntheses of natural products. A precursor of (+)-brefeldin A is synthesized starting from this chiral building block by 10 steps short-cut procedure compared with the shortest method so far reported. (S)-(+)-Sulcatol is obtained in much better enantiomeric purity than those reported. The reactivity of 1 in base-catalyzed condensations with Michael acceptors or aldehydes is largely affected by a base employed as the catalyst.
