Intermediates for the preparation of analogs of halichondrin B

A compound of formula F-1:

• wherein:
• each of PG1 and PG2 is independently a suitable hydroxyl protecting group, taken with the oxygen atom to which it is bound, selected from the group consisting of an acetate, a carbonate, a sulfonate, a silyl ether, an alkyl ether, an arylalkyl ether, and an alkoxyalkyl ether, or PG1 and PG2 are taken together, with the oxygen atoms to which they are bound, to form a diol protecting group;
• R1 is R or OR;
• R2 is CHO or —CH═CH2;
• and
• each R is independently hydrogen, C1-4 haloaliphatic, benzyl, or C1-4 aliphatic, provided that, when R1 is OMe, then PG1 and PG2 do not form an acetonide group, or PG1 and PG2 are H, R1 is OH, and R2 is —CH═CH2.