Viral inhibitors, the synthesis therof, and intermediates thereto

A composition of Compound 1, Compound 2a, Compound 3a, Compound 5a, and Compound 8a, the composition comprising Compound 1, Compound 2a, Compound 3a, Compound 5a, and Compound 8a, having the following structures:

• wherein R1 is an optionally substituted group selected from C1-6 aliphatic, 3- to 7-membered saturated or partially unsaturated carbocyclyl, 3- to 7-membered saturated or partially unsaturated heterocyclyl having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, phenyl, or 5- to 6-membered heteroaryl having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur;
• each R2 is independently a halogen;
• each PG1 is independently an oxygen protecting group;
• and
• X is camphorsulfonic acid (CSA), benzenesulfonic acid (PhSO3H), methanesulfonic acid (MsOH), toluenesulfonic acid (TsOH), 1,5-naphthalenedisulfonic acid (napsylic acid), 1,2-ethanedisulfonic acid (edisic acid), ethanesulfonic acid (esic acid), 4-chlorobenzenesulfonic acid (closic acid), 6,7-dihydroxycoumarin-4-methanesulfonic acid (cromesic acid), trifluoromethanesulfonic acid (HOTf), HF, HCl, HBr, or HI;
• wherein Compound 2a is present in an amount of 0.1% w/w or less relative to Compound 1;
• wherein Compound 3a is present in an amount of 0.1% w/w or less relative to Compound 1;
• wherein Compound 5a is present in an amount of 0.1% w/w or less relative to Compound 1;
• and
• Compound 8a is present in an amount of 0.1% w/w or less relative to Compound 1.