title: Synthesis of hydroxyphthioceranic acid using a traceless lithiation-borylation-protodeboronation strategy.
abstract: In planning organic syntheses, disconnections are most often made adjacent to functional groups, which assist in C-C bond formation. For molecules devoid of obvious functional groups this approach presents a problem, and so functionalities must be installed temporarily and then removed. Here we present a traceless strategy for organic synthesis that uses a boronic ester as such a group in a one-pot lithiation-borylation-protodeboronation sequence. To realize this strategy, we developed a methodology for the protodeboronation of alkyl pinacol boronic esters that involves the formation of a boronate complex with a nucleophile followed by oxidation with Mn(OAc)3 in the presence of the hydrogen-atom donor 4-tert-butylcatechol. Iterative lithiation-borylation-protodeboronation allows the coupling of smaller fragments to build-up long alkyl chains. We employed this strategy in the synthesis of hydroxyphthioceranic acid, a key component of the cell-wall lipid of the virulent Mycobacterium tuberculosis, in just 14 steps (longest linear sequence) with full stereocontrol.
authors.affiliation: School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK.
authors.forename: Ramesh
authors.initials: R
authors.lastname: Rasappan
authors.affiliation: School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK.
authors.forename: Varinder K
authors.initials: VK
authors.lastname: Aggarwal
mesh_terms: D001895:Boron / Q000737:chemistry; D060326:Chemistry Techniques, Synthetic / Q000379:methods*; D008094:Lithium / Q000737:chemistry
chemical_list: D008094:Lithium; D001895:Boron