Table 1.

Side-chain structure of chemically synthesized phycocyanobilin and analogs

Bilins	A-ring			B-ring		C-ring		D-ring		References
	R1*	R2	R3	R4	R5	R6	R7	R8	R9
PCB	CH3	H	CH3	CH3	(CH2)2CO2H	(CH2)2CO2H	CH3	CH3	CH2CH3	15, 16, 21, 23
Analog 1†	H									20
Analog 2	CH2CH3									20
Analog 3		CH3								20
Analog 4			CH2CH3							20
Analog 5					(CH2)2CO2CH3					16
Analog 6						(CH2)2CO2CH3				16
Analog 7				(CH2)2CO2H	CH3					16
Analog 8						CH3	(CH2)2CO2H			16
Analog 9				(CH2)2CO2H	CH3	CH3	(CH2)2CO2H			16
Analog 10					(CH2)3CO2H					16
Analog 11						(CH2)3CO2H				16
Analog 12					(CH2)3CO2H	(CH2)3CO2H				16
Analog 13								CH2CH2CH3	CH3	‡
Analog 14								CH2(CH2)3CH3	CH3	‡
Analog 15								CH2(CH2)6CH3	CH3	‡
PΦB									CH⩵CH2	22
Analog 16									CH2CH2CH3	‡
Analog 17									CH2(CH2)3CH3	‡
Analog 18									CH2(CH2)6CH3	‡
Analog 19									CH2CH2OCOCH3	‡
Analog 20									CH2CH2SC6H4CH3-p	‡

^*R¹–R⁹, side chains of PCB (see Fig. 1). 

^† Analog structures are identical to PCB except where indicated. 

^‡ Present study.