Stereocontrolled transformation of nitrohexofuranoses into cyclopentylamines via 2-oxabicyclo[2.2.1]heptanes. Part 6: synthesis and incorporation into peptides of the first reported 2,3-dihydroxycyclopentanecarboxylic acid
摘要:
Herein we report the intramolecular alkylation of nitronates of methyl-5-O-benzy1-3,6-deoxy-6-nitro-alpha-D-glucofuranoside and methyl-5-O-benzyl-3,6-deoxy-6-nitro-alpha-D-glucofuranoside into the corresponding 2-oxabicyclo[2.2.1]heptane derivatives. Similarly, methyl-3-O-benzy1-5-deoxy-5-nitromethy1-13-beta-D-xylofuranoside and methyl-3-O-benzyl-5-deoxy-5-nitromethyl-alpha-D-xylofuranoside were cyclized to (1R,3R, 45,5R,7R)-7-benzyloxy-3-methoxy-5-nitro-2-oxabicyclo[2.2.1]heptane and (1R,3S,4S,5R,7R)-7-benzyloxy-3-methoxy-5-nitro-2-oxabicyclo[2.2.1]heptane, respectively. These 2-oxabicyclo[2.2.1]heptane derivatives were eventually transformed into enantiopure methyl (15,2S,3R,4S,5R)-2-amino-2,3-dihydroxycyclopentanecarboxylate and this novel beta-amino acid was incorporated into peptides. (c) 2014 Elsevier Ltd. All rights reserved.
Polysubstituted cyclopentane rings can be synthesized with good to high stereocontrol by radical cyclization using tributyltin hydride and a radical initiator, triethylborane–O2 in anhydrous xylene at room temperature. We have demonstrated that the nature (protected or unprotected) of the hydroxy functions in position 2 and 4 is responsible for the stereochemical cyclization outcome of acyclic 1-substituted-2