Assignment of the ¹H and ¹³C NMR spectra, sequence and conformation of the synthetic pentasaccharide SanOrg34006 and its precursors

Abstract

Proton and carbon chemical shift data and proton-proton coupling constants of the synthetic antithrombotic pentasaccharide SanOrg34006 and its synthetic precursors are reported. Long-range heteronuclear correlation experiments allow the determination of the substitution pattern of the protecting groups in the precursor molecules. Also, the sequence of the oligosaccharide was confirmed this way. The conformation of the a-L-iduronic acid moiety was studied by the analysis of the 3 J.

Citronamides A and B, Tetrapeptides from the Australian Sponge Citronia astra

“…Small vicinal couplings between H-24 and H-25 (4.7 Hz in 1 and 4.9 Hz in 2 ) and between H-25 and H-26 (4.7 Hz in 1 and 4.8 Hz in 2 ) together with strong ROESY correlations between H-24 and H-25 and between H-25 and H-26 in 1 suggested that H-25 and H-26 were also equatorial. Furthermore, small COSY correlations observed between H-23 and H-25 and between H-24 and H-26 in both 1 and 2 could be assigned to W couplings that would only be present if these four protons adopted equatorial positions. , H-27 was axial since a weaker ROESY correlation and a small coupling ( J = 2.8 Hz in 1 and 3.3 Hz in 2 ) was observed between H-26 and H-27. The relative configurations assigned to C-25, C-26, and C-27 in 1 were corroborated by the observation of a small ROESY correlation between H-27 and the axial carbamate protons attached to C-25 (δ 6.50, CONH 2 ).…”

“…Furthermore, small COSY correlations observed between H-23 and H-25 and between H-24 and H-26 in both 1 and 2 could be assigned to W couplings that would only be present if these four protons adopted equatorial positions. 12,15 H-27 was axial since a weaker ROESY correlation and a small coupling (J ) 2.8 Hz in 1 and 3.3 Hz in 2) was observed between H-26 and H-27. The relative configurations assigned to C-25, C-26, and C-27 in 1 were corroborated by the observation of a small ROESY correlation between H-27 and the axial carbamate protons attached to C-25 (δ 6.50, CONH 2 ).…”