Glycine → (2S)-2-amino-5-(tert-butoxy)-5-oxopentanoic acid

Participants

Reaction Steps

The inability to crystallize some of the above-mentioned derivatives led to the preparation of corresponding 3,4-dihydro-4-oxo-1,2,3-benzotriazine-3-yl (ODhbt) esters. The Ddz-Xxx-ODhbt esters of Ala, Pro, and Trp were easily prepared as crystalline solids, followed by Gly, Val, and Ile. In addition, the ODhbt esters of Ser and Thr were crystallized upon preparation, whereas Leu, Met, Phe, Cys(Stbu), Asp(tBu), and Glu(tBu) were obtained as foams. Ddz-Arg-(Pmc)Dhbt was isolated in about 92% purity including 5-6% of the γ-lactam impurity. Ddz-Arg(Pmc)Pfp was also isolated, but with somewhat less γ-lactam impurity. Examples of derivatives prepared are summarized in Table 1 and the examples.

Provenance & Evidence