Alkoxycarbonylation and selective deprotection of N-silyl derivatives of L-arginine

New tris-alkoxycarbonyl arginine derivatives for peptide synthesis

alpha-Alkoxycarbonyl protected ornithines were treated with N,N'-[Z(2Cl)](2)-S-methylisothiourea and N,N'-[Z(2Br)](2)-S-methylisothiourea, N,N'-Z(2)-S-methylisothiourea and N,N'-Boc(2)-S-methylisothiourea to form N(alpha, omega, omega')-tris-alkoxycarbonyl arginines. Two of them, Boc-Arg-{omega,omega'-[Z(2Br)](2)}-OH and Boc-Arg-{omega,omega'-[Z(2Cl)](2)}-OH, were used for the synthesis of dermorphin fragments containing two or three arginine residues. Examination of the products by HPLC and ESI-MS revealed that the purity of the materials obtained with the use of the new derivatives was higher than that obtained in concurrent syntheses in which Boc-Arg(Tos) was used.

Synthesis and absolute configuration of Stellettadine A: a marine alkaloid that induces larval metamorphosis in ascidians

Stellettadine A, a bisguanidinium alkaloid isolated from a marine sponge Stelletta sp. as an inducer of larval metamorphosis in ascidians, and its unnatural enantiomer were synthesized from the enantiomers of citronellal. The absolute configuration of stellettadine A was established as R.