Cerium ammonium nitrate: A new catalyst for regioselective protection of glycols
The regioselective introduction of a methoxymethyl (MOM) group on different type of glycols via an orthoester intermediate was investigated. The novelty presented in this study is the use of ceric ammonium nitrate instead of the previously employed camphorsulfonic acid as catalyst. The monoprotection reaction was revealed to be highly selective when the glycol moiety was in the presence of an ether functionality. Graphical abstract
Comin, María J.,Elhalem, Eleonora,Rodriguez, Juan B.
Synthesis, biological evaluation and molecular docking studies of benzyloxyacetohydroxamic acids as LpxC inhibitors
The inhibition of the UDP-3-O-[(R)-3-hydroxymyristoyl]-N-acetylglucosamine deacetylase (LpxC) represents a promising strategy to combat infections caused by multidrug-resistant Gram-negative bacteria In order to elucidate the functional groups being impor
Szermerski, Marina,Melesina, Jelena,Wichapong, Kanin,L?ppenberg, Marius,Jose, Joachim,Sippl, Wolfgang,Holl, Ralph
p. 1016 - 1028
(2014/02/14)
Redesign of enzyme for improving catalytic activity and enantioselectivity toward poor substrates: Manipulation of the transition state
Secondary alcohols having bulky substituents on both sides of the hydroxy group are inherently poor substrates for most lipases. In view of this weakness, we redesigned a Burkholderia cepacia lipase to create a variant with improved enzymatic characteristics. The I287F/I290A double mutant showed a high conversion and a high E value (>200) for a poor substrate for which the wild-type enzyme showed a low conversion and a low E value (5). This enhancement of catalytic activity and enantioselectivity of the variant resulted from the cooperative action of two mutations: Phe287 contributed to both enhancement of the (R)-enantiomer reactivity and suppression of the (S)-enantiomer reactivity, while Ala290 created a space to facilitate the acylation of the (R)-enantiomer. The kinetic constants indicated that the mutations effectively altered the transition state. Substrate mapping analysis strongly suggested that the CH/π interaction partly enhanced the (R)-enantiomer reactivity, the estimated energy of the CH/π interaction being -0.4 kcal mol-1. The substrate scope of the I287F/I290A double mutant was broad. This biocatalyst was useful for the dynamic kinetic resolution of a variety of bulky secondary alcohols for which the wild-type enzyme shows little or no activity. The Royal Society of Chemistry 2012.
Ema, Tadashi,Nakano, Yasuko,Yoshida, Daiki,Kamata, Shusuke,Sakai, Takashi
p. 6299 - 6308
(2012/09/05)
Efficient Preparation of tributylstannane, a Convenient Hydroxymethyl Anion Equivalent
-
Johnson, Carl R.,Medich, John R.
p. 4131 - 4133
(2007/10/02)
ASYMMETRIC REDUCTION OF PROCHIRAL HYDROXY KETONES WITH A CHIRAL REDUCING AGENT PREPARED FROM TIN(II) CHLORIDE, A CHIRAL DIAMINE, AND DIISOBUTYLALUMINUM HYDRIDE
Asymmetric reduction of prochiral α- and β-hydroxy ketones with a reagent, generated from tin(II) chloride, a chiral diamine, and diisobutylaluminum hydride, afforded the corresponding dihydroxy compounds in good chemical and optical yields.Optical yields depended on the nature of the protective groups of hydroxyl function.