Crystal of spiroketal derivatives and process for preparation of spiroketal derivatives

A process for preparing a compound represented by Formula (I):

• wherein n is 0, m is an integer selected from 0 and 1;
• R2 is selected from C1-4 alkyl;
• which comprises:
• Step a):
• treating a compound of Formula (II):
• wherein X1 and X2 are independently selected from a bromine atom or an iodine atom;
• P1 is a metal ion, a hydrogen atom or a protecting group of hydroxy;
• and n is as defined above;
• with an organometal reagent, and then reacting with a compound of Formula (III):
• wherein P2, P3, P4, and P5 are independently selected from a protecting group of hydroxy;
• or P2 and P3, P3 and P4, and P4 and P5 together may independently represent a divalent group to protect two hydroxy groups and to form a ring;
• to obtain a compound represented by Formula (IVa):
• wherein n, X2, P1, P2, P3, P4, Y and P5 are as defined above;
• and
• X is a metal ion, or a hydrogen atom;
• Step b):
• treating a compound represented by Formula (IVb):
• wherein n, X2, P1, P2, P3, P4, and P5 are as defined above;
• and
• P6 is a metal ion, a hydrogen atom or a protecting group of hydroxy;
• with an organometal reagent, and then reacting with a compound represented by Formula (V):
• wherein R42 is a group defined as R2 and m is as defined above;
• and
• which may further comprise one or more steps to introduce a protecting group and/or to remove a protecting group, in the steps defined above and/or in any stage prior to or after any one of the steps defined above.