Lewis acid mediated synthesis of cyclic esters

A method for the diastereoselective preparation of compounds of Formula II:

• wherein:
• V is selected from group consisting of aryl, and monocyclic heteroaryl, all optionally substituted with 1-4 substituents;
• W and W′ are independently selected from the group consisting of H, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted monocyclic aryl, and optionally substituted monocyclic heteroaryl;
• Z is selected from the group consisting of halogen, —CN, —COR3, —CONR42, —CO2R3, —CHR2OC(O)R3, —CHR2OC(S)R3, —CHR2OC(O)SR3, —CHR2OCO2R3, —OR3, —SR3, —R2, —NR32, —OCOR3, —OCO2R3, —SCOR3, —SCO2R3, —(CH2)p—OR4, and —(CH2)p—SR4;
• T is selected from the group consisting of H and lower alkyl;
• R2 is hydrogen or lower alkyl;
• R3 is alkyl;
• R4 is alkyl or acyl;
• p is 2 or 3;
• r is 0 or 1, and
• s is 0 or 1;
• R5is a monovalent amine protecting group, and R6 is hydrogen;
• or,
• R5 and R6 taken together are a divalent amine protecting group;
• the method comprising:
• combining a 1-(V)-1,3-propane diol with a compound of Formula III in the presence of a Lewis acid:
• wherein the ratio of cis- to trans-diastereomers of the compounds of Formula II formed is greater than or equal to 3:1.