Intermediate for preparing eribulin mesylate and process for preparing the same

A process for preparing a compound of the following formula (6), which comprises the steps of:

• (i) subjecting a primary hydroxy group of a compound of the following formula (7) to selective sulfonylation to obtain a compound of the following formula (8);
• (ii) subjecting the compound of the following formula (8) to cyclization to obtain a compound of the following formula (9);
• (iii) subjecting the compound of the following formula (9) to allylation to obtain a compound of the following formula (10);
• (iv) subjecting a hydroxy group of the compound of the following formula (10) to methylation to obtain a compound of the following formula (11);
• (v) subjecting an alkene group of the compound of the following formula (11) to stereoselective dehydroxylation to obtain a compound of the following formula (12);
• (vi) protecting a hydroxy group of the compound of the following formula (12) to obtain a compound of the following formula (13);
• (vii) subjecting the compound of the following formula (13) to Hosomi-Sakurai reaction to obtain a compound of the following formula (14);
• (viii) subjecting an alkene group of the compound of the following formula (14) to dehydroxylation, oxidation and reduction to obtain a compound of the following formula (15);
• (ix) selectively protecting a primary hydroxy group of the compound of the following formula (15) to obtain a compound of the following formula (16);
• (x) oxidizing a hydroxy group of the compound of the following formula (16) to obtain a compound of the following formula (17);
• (xi) subjecting the compound of the following formula (17) to methenylation to obtain a compound of the following formula (18);
• (xii) subjecting the compound of the following formula (18) to hydroboration and oxidation to obtain a compound of the following formula (19);
• (xiii) oxidizing a hydroxy group of the compound of the following formula (19) to obtain a compound of the following formula (20);
• (xiv) subjecting the compound of the following formula (20) to isomerization to obtain a compound of the following formula (21);
• (xv) reducing the compound of the following formula (21) to obtain a compound of the following formula (22);
• (xvi) subjecting a hydroxy group of the compound of the following formula (22) to sulfonylation to obtain a compound of the following formula (23);
• (xvii) substituting a leaving group of the compound of the following formula (23) with a sulfide to obtain a compound of the following formula (24);
• (xviii) selectively deprotecting a benzoyl or acetyl group of the compound of the following formula (24) to obtain a compound of the following formula (25);
• (xix) protecting a hydroxy group of the compound of the following formula (25) to obtain a compound of the following formula (26);
• (xx) deprotecting a pivaloyl group of the compound of the following formula (26) to obtain a compound of the following formula (27);
• and
• (xxi) oxidizing a hydroxy group of the compound of the following formula (27):
• wherein,
• R1 represents a leaving group selected from the group consisting of p-toluenesulfonyl, methanesulfonyl, and trifluoromethanesulfonyl,
• R2 represents benzoyl or acetyl,
• Pv represents pivaloyl,
• Ar represents aryl, and
• R3 represents a silyl protecting group selected from the group consisting of trimethylsilyl (TMS), triethylsilyl (TES), t-butyldimethylsilyl (TBS), and t-butyldiphenylsilyl (TBDPS).