Liquid and solid phase syntheses of orthogonally protected α-hydrazinoacid derivatives
The first solid phase synthesis of chiral α-hydrazinoacids has been developed. This synthesis was achieved by the preparation of solid supported-N-alkyloxycarbonyl-aminophthalimides used as acidic partners in the Mitsunobu protocol involving α-hydroxyesters. Two different final trans-protection steps of the phthaloyl group, developed first in liquid phase, result in efficient releases of orthogonally bis-protected or fully tris-protected hydrazine derivatives. A comparison between liquid and solid phase syntheses is outlined: even if the overall yields are sometimes rather higher by the liquid phase synthesis, the on-resin protocol is much more rapid and convenient than the liquid protocol.
Synthesis of Nα-Z, Nβ-Fmoc or Boc protected α-hydrazinoacids and study of the coupling reaction in solution of Nα-Z-α-hydrazinoesters
The preparation of chiral orthogonally protected Nα-Z, Nβ-Fmoc- or Boc-α-hydrazinoacids derivatives, directly suitable for SPPS, is described in six steps with good yields starting from the corresponding α-aminoacids. The coupling reaction assays performed in liquid phase between Nα-Z-hydrazinoesters and N-Fmoc-α-aminoacids demonstrated the low reactivity of the hydrazinoester derivatives. However, we found that the acid fluoride method allowed the formation of hydrazinodipeptides almost quantitatively.
A practical reagent for the synthesis of substituted hydrazines
A practical, inexpensive triprotected hydrazine reagent, 2-benzyloxycarbonyl-1 -tert-butoxycarbonyl-1- (4-methylphenylsulfonyl)-hydrazine, 1-Boc-1-Tos-2-Z-hydrazine (2), has been prepared on a 100 pnmol scale and examined with respect to application in st
Grehn, Leif,Nyasse, Barthelemy,Ragnarsson, Ulf
p. 1429 - 1432
(2007/10/03)
More Articles about upstream products of 200813-56-5