Correction to Synthesis of Seven-Membered Ring Glycals via endo

Addition/Correction Cite This: Org. Lett. XXXX, XXX, XXX−XXX

pubs.acs.org/OrgLett

Correction to Synthesis of Seven-Membered Ring Glycals via endoSelective Alkynol Cycloisomerization Eva Alcaź ar, Joseph M. Pletcher, and Frank E. McDonald* Org. Lett. 2004, 6 (21), 3877−3880. DOI: 10.1021/ol0483495

W

e write to reassign the stereochemistry of several alkynyl diols prepared by Ohira−Bestmann alkynylation. This

Downloaded via 83.171.253.79 on April 25, 2019 at 23:14:11 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.

also requires correcting the stereochemistry of some of the resulting seven-membered ring glycals. In the Ohira−Bestmann alkynylation (K2CO3, MeOH, MeC(O)C(N2)P(O)(OMe)2, 65 °C) of acetal-protected ribose and lyxose derivatives, we have discovered that one of the chiral centers completely epimerizes, giving the diastereomer at the propargylic carbon. X-ray crystallographic analysis firmly establishes that the stereochemical assignment for benzylidene-protected alkynyldiol is not 10, but its diastereomer A. The corresponding sevenmembered ring glycal is not the cis-fused structure 11, but the trans-fused diastereomer B.

Careful examination of the original spectral tabulations strongly indicates the following stereochemical corrections for compounds 5, 8, 9, 12, 13, 18, and 19, as structures C−I,

We thank Mr. Andrew J. Ephron and Dr. John Bacsa (Emory University) for identifying the epimerization and correcting the stereochemistry of the structures originally claimed as 10 and 11.

respectively. We have determined that regioselectivity for seven-membered ring formation requires trans-orientation of the diol and alkyne substituents on a cyclic 1,3-dioxolane. We will communicate

Received: April 18, 2019

additional details in a future manuscript. © XXXX American Chemical Society

A

DOI: 10.1021/acs.orglett.9b01022 Org. Lett. XXXX, XXX, XXX−XXX