Deoxy-Hexopyranoses

In his total synthesis of the macrolide avermectin Bla, Ley [84] reported the in situ activation of an oleandrose unit (2,6-dideoxy-3-0-methyl-L-ara6i o-hexose) by carbonyldiimidazole or thiocarbonyl-diimidazole to give imidazolylcarbonyl and imidazolyl-thiocarbonyl glycosides respectively which undergo predominant a-glycosylation in the presence of silver perchlorate in tetrahydrofuran. 

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Enzyme and source 5-Amino-S-deoxy- hexopyranose 1,5-Dideoxy- 1,5-iminohexitol Glycosylamine References... 

W. Priebc, G. Grynkiewicz, and N. Neamati, One step C-acylation of glycals and 2-deoxy-hexopyranoses at C-2, Tetrahedron Lett. 33 7681 (1992). 

A total of 27 oligosaccharides composed of hexopyranose, deoxyhexopyranose, deoxyfluoro hexopyranose and 2-acetamido-2-deoxy hexopyranose units have been studied by FAB-m.s.l Structurally significant ions were observed, and the authors suggest that this method will be important for the sequencing of oligosaccharides without prior recourse to deiivatization. 

All derivatives used were prepared by essentially standard literature procedures and had physical constants in accord with previously reported values. Furthermore, the P.M.R. spectra were in each case consistent with the assigned structures. All solutions were concentrated under reduced pressure and m.p. s are uncorrected. (I) 2-Deoxy-D-arafczno-hexopyranose was a commercial sample from Pfanstiehl Lab. Inc., Waukegan, Illinois and was used without further purification. (II) 3, 4, 6-Tri-O-acetyl-D-glucal (1) was a commercial sample from Aldrich Chem. Co., Milwaukee, Wisconsin and was purified by distillation and recrystallized three times from aqueous ethanol. (Ill) 1, 3, 4, 6-tetra-0-acetyl-2-deoxy-a-D-arahino-hexopyranose (4) was prepared by the method of Bonner (11) while the corresponding / -anomer (5) was synthesized following the procedure of Overend, Stacey, and Stanek (47). (IV) 5, 6-Dideoxy-1, 2-0-isopropylidene-a-D-xj/io-hex-5-enofuranose (20) was provided by A. Rosenthal and G. Khan of this Department. 

For reasons which will be discussed later, we were interested in obtaining a detailed analysis of the P.M.R. spectrum of both the a-(2) and j8-(3) anomers of 2-deoxy-D-arahmo-hexopyranose in D20 solution. 

The P.M.R. spectrum of an equilibrated aqueous solution of 2-deoxy-D-arafoino-hexopyranose was first measured by Lenz and Heeschen (37) who reported values for the chemical shifts of the anomeric protons and... 

Figure 3. 100 MHz P.M.R. Spectrum of an equilibrated solution of 2-deoxy-v-snabino-hexopyranose in DtO.

Figure 4. Partial 100 MHz P.M.R. spectra of an equilibrated solution of 2-deoxy-B-siYabmo-hexopyranose in D2O solution (B) normal resonance (A) with irradiation of Ht(a) (C) with irradiation of Hi(fl).

The study of Lemieux and co-workers (38, 39) which first delineated the stereospecific dependences of the P.M.R. parameters of pyranose derivatives has since been confirmed by many workers (24, 40, 44). In the following section we shall discuss some of the more recently recognized stereospecific dependences, dealing first with the dependences of coupling constants and then with those of chemical shifts. Reference will be made to the P.M.R. parameters of the hexopyranose derivatives which were obtained in experiments outlined in the previous section, together with the parameters of the a-(4) and, / -(5) anomers of 1, 3, 4, 6-tetra-0-acetyl-2-deoxy-D-arafoino-hexopyranose. 

Deoxyhex-5-enose derivatives. 120 2-Deoxy-D-arabino-hexopyranose,... 

Deoxy-p-D-xy/o-hexopyranose 2-Deoxy-D-ribo-hexose not 2-deoxy-D-allose not 4-deoxy-p-D-galactopyranose... 

Deoxy-2-phenyl-a-D-glucopyranose or 2-deoxy-2-C-phenyl-a-D-glucopyranose or (2fl)-2-deoxy-2-phenyl-a-D-arab/no-hexopyranose... 

Stereospecific dependencies of the nonselective relaxation-rates for other protons in a sugar molecule may be seen in the data for a set of 3,4,6-tri-O-acetyl-l-0-benzoyl-2-deoxy-2-bromo-D-hexopyranose derivatives (40-42), as well as other 2-halogeno derivatives. A comparison of their... 

T. Komano worked with him. The work accomplished at that time included the following N-debenzyloxycarbonylation of 1,3,4,6-tetra-0-acetyl-2-(benzyloxycarbonyl)amino-2-deoxy-D-hexopyranoses in the conversion of a,/3-acetoxy to glycosyl bromide (1961) oxidative cleavages of 1,2-diamino sugars and their significance in the mechanism of the aminocarbonyl reactions (1962) and synthesis of 2-amino-2-deoxy-/3-o-glucosides via 3,4,6-tri-D-acetyl-2-benzylsulfonamido-2-deoxy-a-D-glu-copyranosyl bromide (1962). 

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