The present invention relates to a process for the preparation of (R) -methyl-2- (3-aminopiperidin- 1 -yl) -3- (2-cyanobenzyl) -4-carbonyl- 2-d] pyrimidine-6-carboxylic acid maleate ((R) -Methyl-2- (3-aminopiperidin-1-yl) -3- (2-cyanobenzyl) -4-carbonyl-3,4-dihydrothiophene [3,2-d] pyrimidine-6-carboxylic acid maleate, and a process for producing the same, wherein the crystalline form is a high-stability and low-hygroscopic crystal, and the crystalline form is a crystalline form A, Is selected. In addition, the crystalline form of the present invention has a relatively strong in-body sugar-lowering activity and can be used in the production of novel drugs for the treatment or prevention of complications of type II diabetes and / or type II diabetes.본 발명은 (R)-메틸-2-(3-아미노피페리딘-1-일)-3-(2-시아노벤질)-4-카르보닐-3,4-디히드로티오펜[3,2-d]피리미딘-6-카르복실산말레산염((R)-Methyl-2-(3-aminopiperidin-1-yl)-3-(2-cyanobenzyl)-4-carbonyl-3,4-dihydrothiophene[3,2-d]Pyrimidine-6-carboxylic acid maleate)의 다결정형 및 이의 제조 방법에 관한 것으로, 상기 결정형은 고 안정성 및 저 흡습성의 결정체이고, 상기 결정형은 결정형 A, 결정형 B 및 결정형 C로부터 선택된다. 또한, 본 발명의 결정형은 비교적 강한 체내 당 강하 활성을 구비하고, II형 당뇨병 및/또는 II형 당뇨병의 합볍증을 치료 또는 예방하기 위한 신규한 약물의 제조에 사용될 수 있다.
