The first preparative solution phase synthesis of melanotan II

• Vladimir V. Ryakhovsky,
• Georgy A. Khachiyan,
• Nina F. Kosovova,
• Elena F. Isamiddinova and
• Andrey S. Ivanov

Beilstein J. Org. Chem. 2008, 4, No. 39, doi:10.3762/bjoc.4.39

• the guanidine group in arginine, it was deactivated as the monohydrochloride salt over the course of 4 steps, and then as trifluoroacetate for another 2 steps. A similar method for arginine deactivation had been applied earlier in the first solution-phase synthesis of ACTH [30]. The assembly of the

• protected dipeptide 6. Since arginine exists in DMF solution in zwitterionic form, no protection for highly basic guanidine group was required. The guanidine group of arginine was deactivated for the next 4 steps by adding an equivalent of HCl (dioxane solution) to dipeptide 6. The resulting salt was

C₂-symmetric bisamidines: Chiral Brønsted bases catalysing the Diels- Alder reaction of anthrones

• Deniz Akalay,
• Gerd Dürner,
• Jan W. Bats and
• Michael W. Göbel

Beilstein J. Org. Chem. 2008, 4, No. 28, doi:10.3762/bjoc.4.28

• exerted by chiral Brønsted bases. Moderate to excellent stereoselectivities of products 3 have been reported using pyrrolidines 4 [1][2], cyclic guanidine 5 [3], or cinchona alkaloids 6 [4] as catalysts. Recently, we could promote this type of cycloaddition by metal-free bisoxazolines 7 in up to 70% ee

Perhalogenated pyrimidine scaffolds. Reactions of 5-chloro- 2,4,6-trifluoropyrimidine with nitrogen centred nucleophiles

• Emma L. Parks,
• Graham Sandford,
• John A. Christopher and
• David D. Miller

Beilstein J. Org. Chem. 2008, 4, No. 22, doi:10.3762/bjoc.4.22

• , many pyrimidine derivatives have been used for various medicinal applications (Figure 1) [1][2][3]. Synthesis of pyrimidine rings most commonly involves cyclocondensation reactions of amidine, guanidine or thiourea derivatives with either 1,3-diketone or 1,3-diester systems [4][5]. However, many of