Novel Syntheses of 2-Butyl-5-chloro-3H-imidazole-4-carbaldehyde: A Key Intermediate for the Synthesis of the Angiotensin II Antagonist Losartan.

Reaction of glycine methyl ester (19) with imidate 18 under carefully optimized conditions allowed preparation of the rather unstable imidazolinone 11 in ca. 90% yield. Reaction of 11 with POCl(3)/DMF followed by aqueous workup gave aldehyde 2, a key intermediate for the synthesis of the angiotensin II antagonist Losartan, in ca.

Peptide synthesis using novel S-sulfocysteine derivatives.

New cysteine S-sulfonate derivatives, Boc-Cys(SO3Na)-ONa 2 and Fmoc-Cys(SO3Na)-ONa 3, were prepared and their utility for peptide synthesis examined. The Fmoc derivative 3 was used in the solid-phase peptide synthesis of Arg8-vasopressin 9 via the Bunte salt 7. Satisfactory S-sulfonate stability was observed when p-cresol scavenged the cleavage from the resin.

4-Methyltrityl (Mtt): a new protecting group for the side chain protection of Asn and Gln in solid-phase peptide synthesis.

The trityl group was recently introduced for the protection of the side chain carboxamide function of asparagine and glutamine. The 4-methyltrityl (Mtt) group, a structural modification of trityl, is presented here and allows more rapid cleavage from the protected peptides. Procedures for the introduction of the group and comparative cleavage reactions are also presented.