Structural analysis of 3-C-phosphonates, -phosphinates, and -phosphine oxides of branched-chain sugars

Abstract

A complete nmr study (1H, 13C, 31P) of twelve 3-C-phosphonates, -phosphinates, and -phosphine oxide derivatives of 3-C-branched-chain pento- and hexo-furanoses is reported. For all compounds the configuration at C3 is determined and, for oxaphospholanes 9 to 12, the configuration at the asymmetric phosphorus atom. The 3T2 conformation of the furanose ring of acyclic derivatives 1 to 8 and the conformationally rigid cis-fused oxaphospholane-furanose bicyclic systems of 9 to 12 have been used to study the 3JPCCH vs. θP.H and 3JPCCC vs. θP.C relationships which are specific to this series of compounds. The use of the ν P=O ir stretching frequency, δ 31P chemical shift, and 1JP.C coupling constant values in structural analysis of C-phosphorus-bearing sugars is also reported and discussed.

Stereochemistry of cycloaddition of (S)-N-(1-phenylethyl)-C-diethoxyphosphorylated nitrone with vinyl acetate. Studies on mutarotation of 3-(O,O-diethylphosphoryl)-5-hydroxyisoxazolidines

“…To confirm this assumption, detailed conformational analyses of pure isoxazolidines 9 were undertaken based on the vicinal coupling constants (Table 1). [29][30][31][32][33][34][35] It appeared that a preferred conformation could only be unambiguously established for the (3R,5S)-9b diastereoisomer only. The isoxazolidine ring in (3R,5S)-9b adopts an 4 E conformation having the P(O)(OEt) 2 and OAc groups in pseudoequatorial and axial positions, respectively (Fig.…”

Stereoselective synthesis of β-functionalized α-aminophosphonates via aziridinium ions

“…The phosphonates 7 -11 exist almost exclusively as single conformers having the phenyl and phosphonate groups antiperiplanar ( 3 J P -C ipso ¼10.9 -14.3 Hz, 17 3 J H1 -H2 ¼8.1 -11.7 Hz, 18 3 J P -H2 ¼9.0 -12.6 Hz 19 ). Thus, transformation of anti 16 diastereoisomer 6 into anti diastereoisomers 7 -11 requires two inversions of configuration to occur, undoubtedly through the participation of the aziridinium ion 12 (Scheme 3).…”

Nucleophilic Additions to N‐Glycosylnitrones. Asymmetric Synthesis of α‐Aminophosphonic Acids

“…J(H,,P) expected for conformer G [29] is [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] Hz.…”