title: [Au]/[Ag]-catalysed expedient synthesis of branched heneicosafuranosyl arabinogalactan motif of Mycobacterium tuberculosis cell wall.
abstract: Emergence of multidrug-resistant and extreme-drug-resistant strains of Mycobacterium tuberculosis (MTb) can cause serious socioeconomic burdens. Arabinogalactan present on the cellular envelope of MTb is unique and is required for its survival; access to arabinogalactan is essential for understanding the biosynthetic machinery that assembles it. Isolation from Nature is a herculean task and, as a result, chemical synthesis is the most sought after technique. Here we report a convergent synthesis of branched heneicosafuranosyl arabinogalactan (HAG) of MTb. Key furanosylations are performed using [Au]/[Ag] catalysts. The synthesis of HAG is achieved by the repetitive use of three reactions namely 1,2-trans furanoside synthesis by propargyl 1,2-orthoester donors, unmasking of silyl ether, and conversion of n-pentenyl furanosides into 1,2-orthoesters. Synthesis of HAG is achieved in 47 steps (with an overall yield of 0.09%) of which 21 are installation of furanosidic linkages in a stereoselective manner.
authors.affiliation: Department of Chemistry, Indian Institute of Science Education and Research, Dr Homi Bhabha Road, Pune, Maharashtra 411 008, India.
authors.forename: Shivaji A
authors.initials: SA
authors.lastname: Thadke
authors.affiliation: Department of Chemistry, Indian Institute of Science Education and Research, Dr Homi Bhabha Road, Pune, Maharashtra 411 008, India.
authors.forename: Bijoyananda
authors.initials: B
authors.lastname: Mishra
authors.affiliation: Department of Chemistry, Indian Institute of Science Education and Research, Dr Homi Bhabha Road, Pune, Maharashtra 411 008, India.
authors.forename: Maidul
authors.initials: M
authors.lastname: Islam
authors.affiliation: Department of Chemistry, Indian Institute of Science Education and Research, Dr Homi Bhabha Road, Pune, Maharashtra 411 008, India.
authors.forename: Sandip
authors.initials: S
authors.lastname: Pasari
authors.affiliation: Department of Chemistry, Indian Institute of Science Education and Research, Dr Homi Bhabha Road, Pune, Maharashtra 411 008, India.
authors.forename: Sujit
authors.initials: S
authors.lastname: Manmode
authors.affiliation: Department of Chemistry, Indian Institute of Science Education and Research, Dr Homi Bhabha Road, Pune, Maharashtra 411 008, India.
authors.forename: Boddu Venkateswara
authors.initials: BV
authors.lastname: Rao
authors.affiliation: Department of Chemistry, Indian Institute of Science Education and Research, Dr Homi Bhabha Road, Pune, Maharashtra 411 008, India.
authors.forename: Mahesh
authors.initials: M
authors.lastname: Neralkar
authors.affiliation: Department of Chemistry, Indian Institute of Science Education and Research, Dr Homi Bhabha Road, Pune, Maharashtra 411 008, India.
authors.forename: Ganesh P
authors.initials: GP
authors.lastname: Shinde
authors.affiliation: Department of Chemistry, Indian Institute of Science Education and Research, Dr Homi Bhabha Road, Pune, Maharashtra 411 008, India.
authors.forename: Gulab
authors.initials: G
authors.lastname: Walke
authors.affiliation: Department of Chemistry, Indian Institute of Science Education and Research, Dr Homi Bhabha Road, Pune, Maharashtra 411 008, India.
authors.forename: Srinivas
authors.initials: S
authors.lastname: Hotha
mesh_terms: D002384:Catalysis; D002473:Cell Wall / Q000737:chemistry*; D005685:Galactans / Q000138:chemical synthesis*; D006046:Gold / Q000737:chemistry*; D009169:Mycobacterium tuberculosis / Q000737:chemistry*; D012834:Silver / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D005685:Galactans; D012834:Silver; D006046:Gold; C005653:arabinogalactan