title: Enantioselective Syntheses of Lignin Models: An Efficient Synthesis of β-O-4 Dimers and Trimers by Using the Evans Chiral Auxiliary.
abstract: We describe an efficient five-step, enantioselective synthesis of (R,R)- and (S,S)-lignin dimer models possessing a β-O-4 linkage, by using the Evans chiral aldol reaction as a key step. Mitsunobu inversion of the (R,R)- or (S,S)-isomers generates the corresponding (R,S)- and (S,R)-diastereomers. We further extend this approach to the enantioselective synthesis of a lignin trimer model. These lignin models are synthesized with excellent ee (>99 %) and high overall yields. The lignin dimer models can be scaled up to provide multigram quantities that are not attainable by using previous methodologies. These lignin models will be useful in degradation studies probing the selectivity of enzymatic, microbial, and chemical processes that deconstruct lignin.
authors.affiliation: Center for Renewable Carbon, University of Tennessee, Knoxville, TN, 37996, USA.
authors.forename: Costyl N
authors.initials: CN
authors.lastname: Njiojob
authors.affiliation: Center for Renewable Carbon, University of Tennessee, Knoxville, TN, 37996, USA. jbozell@utk.edu.
authors.forename: Joseph J
authors.initials: JJ
authors.lastname: Bozell
authors.affiliation: Department of Chemistry, University of Tennessee, Knoxville, TN, 37996, USA.
authors.forename: Brian K
authors.initials: BK
authors.lastname: Long
authors.affiliation: Southern Research Station, USDA Forest Service, Auburn, AL, 36849, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Elder
authors.affiliation: Center for Renewable Carbon, University of Tennessee, Knoxville, TN, 37996, USA.
authors.forename: Rebecca E
authors.initials: RE
authors.lastname: Key
authors.affiliation: Center for Renewable Carbon, University of Tennessee, Knoxville, TN, 37996, USA.
authors.forename: William T
authors.initials: WT
authors.lastname: Hartwig
mesh_terms: D055598:Chemical Phenomena; D008031:Lignin / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*
chemical_list: D011108:Polymers; D008031:Lignin
keywords: aldol reaction; asymmetric synthesis; biomass; enantioselectivity; natural products