Process for purification of protected polycyclic carbamoylpyridone derivatives

A process for purification of protected tricyclic carbamoylpyridone derivatives of Formula II,

• or a stereoisomer thereof;
• wherein,
• P is a hydroxy protecting group and is one of a straight or branched chain C1-8 alkyl, C1-8 halo alkyl, or substituted or unsubstituted silyl or C6-14 aryl;
• Ar is aryl substituted with one to three halogens;
• V1 and V2 are each independently, hydrogen, a C1-6 alkyl, or a C1-6 haloalkyl;
• or V1 and V2 together with the carbon atom to which they are attached, form a carbocyclic ring having from 3 to 6 ring atoms or a heterocyclic ring having from 3 to 6 ring atoms, wherein the carbocyclic or a heterocyclic ring is optionally substituted with one or more Ra group;
• X is —O—;
• Y is —CH(V5)—;
• Z is a bond, (—CH2—)n or Y and Z taken together form (—CH2—)n;
• wherein n is an integer of 0 to 3;
• V3 and V5 are each independently, hydrogen, a C1-6 alkyl, or a C6-14 aryl;
• or V3 and V5 taken together form a carbocyclic ring containing having from 3 to 6 ring atoms or a heterocyclic ring having from 3 to 6 ring atoms, wherein the carbocyclic or heterocyclic ring is optionally substituted with one or more Ra group, wherein each Ra is, independently, hydrogen, halo, hydroxyl or C1-6 alkyl, or wherein two Ra groups together with the carbon atom to which they are attached to form ═O;
• the process comprising:
• a) reacting a compound of Formula II comprising a compound of Formula III,
• wherein P, Ar, V1, V2, V3, X, Y and Z are as defined above, with a C4-C20 substituted or unsubstituted cyclic anhydride in a suitable solvent;
• b) treating the reaction mass with an aqueous basic solution;
• and
• c) isolating the compound of Formula II substantially free of the compound of Formula III.