Starting material, for bulk drug or additives for drug, and bulk drug or drug using same

A raw material for bulk drugs or a pharmaceutical additive, comprising:

• a polyether composition (A) represented by formula (1),
• wherein the polyether composition (A) has a unimodal molecular weight distribution,
• the polyether composition (A) has a ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of 1.20 or less, and
• the polyether composition (A) contains a compound in which m is 1 in formula (1) in an amount of 90 wt % or more based on the weight of the polyether composition (A),
• in formula (1), OR1, R2O, R3O, and R4O are each independently a C2-C8 oxyalkylene group;
• when each of these moieties exists in the plural number, each OR′, each R2O, each R3O, and each R4O may be the same as or different from each other;
• these moieties may be bonded randomly or in block;
• a, b, c, and d are each independently an integer of 50 to 1200;
• X1 to X4 are each independently a hydrogen atom, a substituent represented by formula (2), or a substituent represented by formula (3);
• and m is an integer of 1 to 10,
• in formulas (2) and (3), R6 is a C1-C10 alkylene group;
• in formula (2), R7 is a hydrogen atom or a C1-C15 monovalent hydrocarbon group in which a hydrogen atom may be replaced by a C1-C10 alkoxy group;
• and when a substituent represented by formula (2) or (3) exists in the plural number in formula (1), each R6 and each R7 in these substituents may be the same as or different from each other.