Plant peptide hormone phytosulfokine (PSK-α):: Synthesis of new analogues and their biological evaluation

Phytosulfokine-alpha (PSK-alpha), a sulfated growth factor (H-Tyr(SO3H)-Ile-Fyr(SO3H)-Thr-Gln-OH) universally found in both monocotyledons and dicotyledons, strongly promotes proliferation of plant cells in culture. In our studies on structure/activity relationship in PSK-alpha the synthesis of a series of analogues was performed: [H-D-Tyr(SO3H)(1)]- (9), [H-Phe(4-SO3H)(1)](-) (10), [H-D-Phe(4- SO3H)(1)]- (11), [H-Phg(4-SO3H)(1)]- (12), [H-D-Phg(4-SO3H)(1)]- (13), [H-Phe(4-NHSO2CH3)(1)]- (14), [H-D-Phe(4-NHSO2CH3)(1)]- (15), [H-Phe(4-NO2)(1)]- (16), [H-D-Phe(4-NO2)(1)]- (17), [H-Phg(4-NO2)(1)]- (18), [H-D-Phg(4-NO2)(1)]- (19), [H-Hph(4-NO2)(1)]- (20), [HPhg(4-OSO3H)(1)]- (21), [Phe(4-NO2)(3)]- (22), [Phg(4-NO2)(3)]- (23), [Hph(4-NO2)(3)]- (24), [H-Phe(4-SO3H)(1), Phe(4-SO3H)(3)]- (25) [H-Phc(4-NO2)(1), Phe(4-NO2)(3)]- (26), [H-Phg(4-NO2)(1), Phg(4-NO2)(3)]- (27), [H-Hph(4-NO2)(1), Hph(4-NO2)(3)]- (28) and [Val(3)]- PSK-alpha (29). For modification of the PSK-alpha peptide chain the novel amino acids and their derivatives were synthesized, such as: H-L-Phg(4-SO3H)-OH (1), H-D-Phg(4-SO3H)-OH (2), Fmoc-Phg(4-SO3H)-OH (3), Fmoc-D-Phg(4-SO3H)-OH (4), Boc-Phg(4-NHSO2CH3)-OH (5), Boc-D-Phg(4NHSO(2)CH(3))-OH (6) Boc-Phe(4-NHSO2CH3)-OH (7), and Boc-D-Phe(4-NHSO2CH3)-OH (8). Peptides were synthesized by a solid phase method according to the Fmoc procedure on a Wang-resin. Free peptides were released from the resin by 95% TFA in the presence of EDT. All peptides were tested by competitive binding assay to the carrot membrane using H-3-labelled PSK according to the Matsubayashi et at. test. Copyright (C) 2004 European Peptide Society and John Wiley Sons, Ltd.