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2004
Peptides
U 0400
44- 217
Hexafluoroacetone as Protecting and Activating Reagent. A New Approach to
N-Linked Glycopeptoids. — Employing hexafluoroacetone (II) as protecting and
activating reagent enables the synthesis of N-glycosylated tripeptoids such as (X) in
five steps with an overall yield of 12-23%, starting from iminodiacetic acid (I). The
procedure includes simultaneous functionalization of the imino and one of the carboxy
groups. From dielectrophile (IV), two regioselective acylation steps can be carried out.
The weak nucleophile (V) reacts with (IV) in the presence of a tert-base to give the
N-glycosylated and α-carboxy activated glycine derivative (VI). Compounds like (VI)
can be used as acyl transfer reagents for amino acid esters and amides providing dipeptoids and dipeptides in good yields. The cleavage of the lactone ring in protected amino
acid (VI) is coupled with the deprotection of the α-amino group, cf. (VI)→(VIII),
allowing elongation of the peptoid chain in N-terminal position without the need for
further deprotection. — (BURGER*, K.; BOETTCHER, C.; HENNIG, L.; ESSAWY,
S. A.; Monatsh. Chem. 135 (2004) 7, 865-877; Fachbereich Chem., Univ. Leipzig,
D-04103 Leipzig, Germany; Eng.) — H. Hoennerscheid
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