Compound exhibiting enteropeptidase inhibitory activity

A compound having the following Chemical Formula 1a or 1b, an optical isomer thereof, or a pharmaceutically acceptable salt thereof:

• wherein,
• A1, A2, A3, A4 and A5 are each independently C;
• Q is O or N;
• R1 and R6 are each independently H or an unsubstituted or substituted alkyl, or R1 and R6 together with the nitrogen atom to which they are attached form an unsubstituted or substituted 5- to 7-membered heterocyclic ring;
• R3 and R4 are each independently H, halo or an unsubstituted or substituted alkyl;
• and
• R5 is amidine or guanidine
• wherein,
• A1, A2, A3, A4, A5, A6, A7 and A8 are each independently C;
• Q is O or N;
• R1 and R6 are each independently H, an unsubstituted or substituted alkyl, or R1 and R6 together with the nitrogen atom to which they are attached form an unsubstituted or substituted 5- to 7-membered heterocyclic ring;
• R2 is H or an unsubstituted or substituted alkyl;
• R3 and R4 are each independently H, halo or an unsubstituted or substituted alkyl;
• and
• R5 is amidine or guanidine,
• the dotted line represents the presence or absence of a bond, and when the bond is present, either a double bond forms between the N in the 5-membered heterocycle and the carbon atom between S and N and the exocyclic nitrogen atom N of NR1R6 becomes an amino group as a substituent for the 5-membered hetero ring and R2 is not present, or a double bond forms between the carbon atom between S and N in the 5-membered heterocycle and the exocyclic nitrogen atom, so that the exocyclic nitrogen atom becomes an imino group and R6 is not present;
• wherein the substituent in any of formula 1a and 1b is one to three selected from the group consisting of —(CRa2)nRb, —C(O)ORa, —(CH2)n—C(O)ORa, —(CH2)n—C(O)NRaRb, —C(O)NRaRb, and —NRaC(O)Rb, where Ra and Rb are each independently hydrogen, halo, —C(O)ORc, C1-C4 alkyl or phenyl, n is an integer from 1 to 4, the C1-C4 alkyl or phenyl is unsubstituted or substituted with one or two —C(O)ORc, or C1-C4 alkoxy, and Rc is hydrogen, C1-C4 alkyl or benzyl.