Reductive Ring Opening of o-Nitrobenzylidene Acetals of Monosaccharides:  Synthesis and Photolysis of Some Photolabile Sugars

Abstract

[figure: see text] A 6-O-o-nitrobenzyl methylglucoside and methylmannoside were synthesized by reacting 4,6-O-o-nitrobenzylidene acetals with triethylsilane and boron trifluoride etherate. A 2,6-di-O-o-nitrobenzyl and a 3,6-di-O-o-nitrobenzyl methylmannoside were obtained from a 2,3:4,6-di-O-o-nitrobenzylidene methylmannoside by the same method. The photolabile sugars obtained were deprotected by irradiation at 350 nm to afford methylglycosides.

1‐(o‐Nitrophenyl)‐2,2,2‐trifluoroethyl Ether Derivatives as Stable and Efficient Photoremovable Alcohol‐Protecting Groups

“…The synthesis of the NPT and DMNPT ether derivatives required for the photochemical study is outlined in Scheme . The direct synthesis of the galactosides through selective opening of cyclic 4,6‐acetals, previously described for the modification of glycosides at C4 by an o ‐nitrobenzyl group,8b failed in our hands in this series. The synthesis of the 4‐substituted galactoside derivative required the use of a glucoside22 corresponding to the epimer of 8 at C4 to take into account the inversion of configuration that occurs during Mitsunobu coupling.…”

“…The synthesis of ether derivatives in the o ‐nitrobenzyl series required the design of an individual methodology for each compound. 2‐ O ‐(2‐Nitrobenzyl)‐ D ‐glucose was synthesized by alkylating a dibutylstannylidene glucose derivative with o ‐nitrobenzyl bromide in moderate yield,8a whereas in two other examples a Lewis acid catalyzed reductive ring opening of a cyclic acetal8b or ketal9 was used to generate 6‐ O ‐(2‐nitrobenzyl) methylglucoside or o ‐nitrobenzyl choline ether derivatives, respectively. As for their photochemical properties, product quantum yields were 0.63 and 0.27 for the 2‐ O ‐(2‐nitrobenzyl)‐ D ‐glucose8a and the O ‐[1‐(2‐nitrophenyl)ethyl]choline9 ether derivatives, respectively.…”

Photochemistry of 2-Nitroarenes: 2-Nitrophenyl-α-trifluoromethyl Carbinols as Synthons for Fluoroorganics

“…The rich photochemistry of o -nitrobenzylic systems has been extensively explored and utilized in the past few decades for convenient application as effective photoremovable protecting groups, − which make these systems a vital tool in chemical biology such as DNA polymerase technology and in the synthesis of photolabile caged compounds. − o -Nitrobenzylic group has been effectively used for the safe photochemical release of acids, alcohols, amines, phosphates, and ketones. In solid state peptide synthesis, it has been used as a very efficient photocleavable protecting group.…”

Synthetic Strategies for Modified Glycosphingolipids and Their Design as Probes

“…Although this method has not been applied to the synthesis of caged glycolipids, the primary hydroxyl group of the Cer moiety was not involved and could likely tolerate a glycan. Photocaged glycan residues have been generated using o -nitrobenzyl groups incorporated into the C-6 of methyl glucoside and methyl mannoside from their 4,6- O - o -benzylidene acetals through reductive ring-opening ( 86 ) . A trifunctional sphingosine probe was made containing a photocleavable caging group, a bioorthogonal alkyne, and a photo-cross-linking diazirine group ( 87 ) …”