ja7b03198_si_001.pdf (6.58 MB)
Regiodivergent Glycosylations of 6‑Deoxy-erythronolide B and Oleandomycin-Derived Macrolactones Enabled by Chiral Acid Catalysis
journal contribution
posted on 2017-06-16, 20:34 authored by Jia-Hui Tay, Alonso J. Argüelles, Matthew D. DeMars, Paul M. Zimmerman, David H. Sherman, Pavel NagornyThis work describes the first example
of using chiral catalysts
to control site-selectivity for the glycosylations of complex
polyols such as 6-deoxyerythronolide B and oleandomycin-derived
macrolactones. The regiodivergent introduction of sugars at
the C3, C5, and C11 positions of macrolactones was achieved by selecting
appropriate chiral acids as catalysts or through introduction of stoichiometric
boronic acid-based additives. BINOL-based chiral phosphoric acids
(CPAs) were used to catalyze highly selective glycosylations
at the C5 positions of macrolactones (up to 99:1 rr), whereas the
use of SPINOL-based CPAs resulted in selectivity switch and glycosylation
of the C3 alcohol (up to 91:9 rr). Additionally, the C11 position
of macrolactones was selectively functionalized through traceless
protection of the C3/C5 diol with boronic acids prior to glycosylation.
Investigation of the reaction mechanism for the CPA-controlled glycosylations
revealed the involvement of covalently linked anomeric phosphates
rather than oxocarbenium ion pairs as the reactive intermediates.
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Keywords
chiral acidsC 11 positionsmacrolactoneRegiodivergent GlycosylationsOleandomycin-Derived Macrolactones EnabledrrSPINOL-based CPAsglycosylreaction mechanismC 5 positionsanomeric phosphatesintroductionC 3 alcoholboronic acidschiral catalyststraceless protectionC 11 positioncontrol site-selectivityBINOL-based chiral phosphoric acidsreactive intermediatesselectivity switch
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