Methods of enhancing sweet taste of compositions using substituted thieno{2,3-D}pyrimidines

A method of enhancing the sweet taste of a comestible composition comprising contacting the comestible composition with a compound of Formula (IIa):

• or a pharmaceutically acceptable salt thereof;
• wherein:
• A is hydrogen, alkyl, substituted alkyl, aryl, substituted aryl, arylalkyl, substituted arylalkyl, heteroaryl, substituted heteroaryl, heteroarylalkyl, substituted heteroarylalkyl, —CN, —OR9, —S(O)cR9, —NR9COR10, —NHOR9, —NR9R10, —CONR9R10, —CO2R9, —NR9CO2R10, —NR9CONR10R11, —NR9CSNR10R11, or —NR9C(═NH)NR10R11;
• R17 is hydrogen, alkyl, or substituted alkyl;
• B is —N—;
• Y forms a single bond with W and a double bond with Z;
• W is —S—;
• Y is —C(R26)—;
• Z is —C(R27)—;
• R26 is hydrogen, alkyl, substituted alkyl, aryl, substituted aryl, arylalkyl, substituted arylalkyl, acyl, substituted acyl, heteroalkyl, substituted heteroalkyl, heteroaryl, substituted heteroaryl, heteroarylalkyl, substituted heteroarylalkyl, —OR31, —OCOR31, —NR31R32, —CONR31R32, or —CO2R31;
• R27 is hydrogen, alkyl, substituted alkyl, aryl, substituted aryl, arylalkyl, substituted arylalkyl, acyl, substituted acyl, heteroalkyl, substituted heteroalkyl, heteroaryl, substituted heteroaryl, heteroarylalkyl, substituted heteroarylalkyl, —OR33, —OCOR33, —NR33R34, —CONR33R34, or —CO2R33;
• R9, R10, R11, R19, R31, R32, R33, and R34 are independently hydrogen, alkyl, substituted alkyl, aryl, substituted aryl, arylalkyl, substituted arylalkyl, heteroalkyl, substituted heteroalkyl, heteroaryl, substituted heteroaryl, heteroarylalkyl or substituted heteroarylalkyl;
• alternatively R9 and R10, R10 and R11, R31 and R32, or R33 and R34, together with the atoms to which they are bonded, form a cycloheteroalkyl or substituted cycloheteroalkyl ring;
• wherein the substituted acyl, substituted alkyl, substituted cycloheteroalkyl, substituted aryl, substituted arylalkyl, substituted heteroalkyl, substituted heteroaryl, and substituted heteroarylalkyl, and substituted cycloheteroalkyl each independently comprises one or more substituent groups selected from the group consisting of —Ra, halo, ═O, —ORb, —SRb, ═S, —NRcRc, ═NRb, ═N—ORb, trihalomethyl, —CN, —NO2, —S(O)2Rb, —S(O)2NRb, —S(O)2ORb, —OS(O)2Rb, —OS(O)2ORb, —P(O)(ORb)(ORb), —C(O)Rb, —C(NRb)Rb, —C(O)ORb, —C(O)NRcRc, —C(NRb)NRcRc, —OC(O)Rb, —OC(O)ORb, —NRbC(O)Rb, —NRbC(O)ORb, —NRbC(O)NRcRc, —NRbC(NRb)Rb and —NRbC(NRb)NRcRc, where Ra is selected from the group consisting of alkyl, cycloalkyl, heteroalkyl, cycloheteroalkyl, aryl, arylalkyl, heteroaryl and heteroarylalkyl;
• each Rb is independently hydrogen or Ra;
• and each Rc is independently Rb or alternatively, the two Rcs are taken together with the nitrogen atom to which they are bonded form a 4-, 5-, 6- or 7-membered cycloheteroalkyl;
• and
• the comestible composition comprises at least one sweetener selected from the group consisting of sucrose and sucralose.