- Enantioselective cyclopropanation of conjugated cyanosulfones using carbohydrate-based crown ether catalysts
-
A few new D-galactose- and D-glucose-based monoaza-15-crown-5 type lariat ethers have been synthesized. These macrocycles and their derivatives proved to be efficient catalysts in the cyclopropanation of (E)-3-phenyl-2-(phenylsulfonyl)acrylonitrile performed with diethyl bromomalonate under mild phase transfer conditions. Among the catalysts tested, the macrocycle having methyl α-D-galactopyranoside unit generated the highest asymmetric induction (80% ee). In the reactions of the aryl-substituted phenylsulfonyl-acrylonitrile derivatives, the cyclopropanation of the meta- and para-substituted starting materials took place with high ee values (75–84% ee). The cyclopropane derivatives synthesized from analogous α,β-unsaturated cyanosulfones containing naphthyl, pyridyl, furyl and thienyl groups were obtained with enantioselectivities up to 85%, and in excellent yields.
- Nemcsok, Tamás,Rapi, Zsolt,Bagi, Péter,Guan, Ying Hou,Orbán, István,Keglevich, Gy?rgy,Bakó, Péter
-
-
- Enzymatic glucosylation of unnatural naphthols by a promiscuous glycosyltransferase from Aloe arborescens
-
Enzymatic glucosylation of unnatural products by natural glycosyltransferases (GTs) has great potential in creating novel and bioactive glucosides. A new GT (AaGT3) from Aloe arborescens exhibited catalytic promiscuity and high efficiency to diverse unnatural naphthols. By combing the substrate flexibility and catalytic reversibility of AaGT3, a cost-effective enzymatic approach to novel and bioactive unnatural glucosides was established. These studies indicate the significant potential of promiscuous natural GTs in synthesis of unnatural bioactive glucosides in drug discovery.
- Xie, Kebo,Zhang, Yujiao,Chen, Ridao,Chen, Dawei,Yang, Lin,Liu, Xia,Dai, Jungui
-
supporting information
p. 2118 - 2121
(2017/05/09)
-
- On the regioselectivity of the protease subtilisin towards the acylation of enantiomeric pairs of benzyl and naphthyl glycopyranosides. Part 2
-
Subtilisin-catalyzed esterification of several enatiomeric benzyl and naphthyl glycopyranosides has been investigated. The D-sugar derivatives were all good substrates and subtilisin regioselectivity was similar with all the compounds tested, the 3-OH being acylated predominantly. On the other hand, most of the L-glycopyranosides were transformed during longer reaction times with a lower regioselectivity, the 2-OH being preferentially but not exclusively acylated.
- Danieli, Bruno,Peri, Francesco,Roda, Gabriella,Carrea, Giacomo,Riva, Sergio
-
p. 2045 - 2060
(2007/10/03)
-
- Non-amphiphilic carbohydrate liquid crystals containing an intact monosaccharide moiety
-
A chiral rigid moiety which forms the basis of a new class of non-amphiphilic carbohydrate liquid crystals has been developed. This moiety contains a fully intact glucopyranose ring embedded in a trans-decalin structure. The original carbohydrate is substituted so that only two hydroxyl groups are left, resulting in derivatives with reduced hydrophilicity. The substituents R and X-R′ on the 4,6-O-ylidene β-D-glucopyranoside are in the equatorial position and can be varied extensively, using straightforward synthetic procedures. Investigations as to the requirements for R and X-R′ for inducing liquid-crystalline behavior have shown that at least one of the substituents should contain a large, polarizable aromatic moiety. An aromatic Schiff base fulfils this requirement.
- Smits,Engberts,Kelogg,Van Doren
-
p. 185 - 199
(2007/10/02)
-
