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

Phytosulfokine‐α (PSK‐α), a sulfated growth factor (H‐Tyr(SO 3 H)‐Ile‐Tyr(SO 3 H)‐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‐α the synthesis of a series of analogues was performed: [H‐ D ‐Tyr(SO 3 H) 1 ]‐ ( 9 ), [H‐Phe(4‐SO 3 H) 1 ]‐ ( 10 ), [H‐ D ‐Phe(4‐SO 3 H) 1 ]‐ ( 11 ), [H‐Phg(4‐SO 3 H) 1 ]‐ ( 12 ), [H‐ D ‐Phg(4‐SO 3 H) 1 ]‐ ( 13 ), H‐Phe(4‐NHSO 2 CH 3 ) 1 ]‐ ( 14 ), [H‐ D ‐Phe(4‐NHSO 2 CH 3 ) 1 ]‐ ( 15 ), [H‐Phe(4‐NO 2 ) 1 ]‐ ( 16 ), [H‐ D ‐Phe(4‐NO 2 ) 1 ]‐ ( 17 ), [H‐Phg(4‐NO 2 ) 1 ]‐ ( 18 ), [H‐ D ‐Phg(4‐NO 2 ) 1 ]‐ ( 19 ), [H‐Hph(4‐NO 2 ) 1 ]‐ ( 20 ), [H‐Phg(4‐OSO 3 H) 1 ]‐ ( 21 ), [Phe(4‐NO 2 ) 3 ]‐ ( 22 ), [Phg(4‐NO 2 ) 3 ]‐ ( 23 ), [Hph(4‐NO 2 ) 3 ]‐ ( 24 ), [H‐Phe(4‐SO 3 H) 1 , Phe(4‐SO 3 H) 3 ]‐ ( 25 ) [H‐Phe(4‐NO 2 ) 1 , Phe(4‐NO 2 ) 3 ]‐ ( 26 ), [H‐Phg(4‐NO 2 ) 1 , Phg(4‐NO 2 ) 3 ]‐ ( 27 ), [H‐Hph(4‐NO 2 ) 1 , Hph(4‐NO 2 ) 3 ]‐ ( 28 ) and [Val 3 ]‐ PSK‐α ( 29 ). For modification of the PSK‐α peptide chain the novel amino acids and their derivatives were synthesized, such as: H‐ L ‐Phg(4‐SO 3 H)‐OH ( 1 ), H‐ D ‐Phg(4‐SO 3 H)‐OH ( 2 ), Fmoc‐Phg(4‐SO 3 H)‐OH ( 3 ), Fmoc‐ D ‐Phg(4‐SO 3 H)‐OH ( 4 ), Boc‐Phg(4‐NHSO 2 CH 3 )‐OH ( 5 ), Boc‐ D ‐Phg(4‐NHSO 2 CH 3 )‐OH ( 6 ) Boc‐Phe(4‐NHSO 2 CH 3 )‐OH ( 7 ), and Boc‐ D ‐Phe(4‐NHSO 2 CH 3 )‐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 3 H‐labelled PSK according to the Matsubayashi et al. test. Copyright © 2004 European Peptide Society and John Wiley & Sons, Ltd.