Oxetane amino acids: synthesis of tetrameric and hexameric carbopeptoids derived from l-ribo 4-(aminomethyl)-oxetan-2-carboxylic acid

The synthesis of methyl 2,4-anhydro-5-azido-3-O-benzyl-5-deoxy-l-ribonate, a δ-2,4-cis-oxetane-azido ester scaffold derived from l-arabinose, is reported. Iterative coupling methods were utilised to form homo-oligomers up to the hexamer in order to investigate the secondary structural preferences of these systems.

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5-Azido-3-O-benzyl-5-deoxy-1,2-O-isopropylidene-β-l-arabinofuranoseC15H19N3O4Ee = 100%[α]D23=-55.8 (c 1.1, CHCl3)Source of chirality: l-arabinose as starting material

5-Azido-3-O-benzyl-5-deoxy-l-arabinono-1,4-lactoneC12H13N3O4Ee = 100%[α]D23=-158 (c 1.16, CHCl3)Source of chirality: l-arabinose as starting material

Methyl 2,4-anhydro-5-azido-3-O-benzyl-5-deoxy-l-ribonateC13H15N3O4Ee = 100%[α]D23=-169 (c 1.25, CHCl3)Source of chirality: l-arabinose as starting material

Isopropyl 2,4-anhydro-5-azido-3-O-benzyl-5-deoxy-l-ribonateC15H19N3O4Ee = 100%[α]D23=-160 (c 1.5, CHCl3)Source of chirality: l-arabinose as starting material

Isopropyl 2,4-anhydro-5-(2,4-anhydro-5-azido-3-O-benzyl-5-deoxy-l-ribononamido)-3-O-benzyl-5-deoxy-l-ribonateC17H32N4O7Ee = 100%[α]D23=-87.7 (c 0.71, CHCl3)Source of chirality: l-arabinose as starting material

Isopropyl 2,4-anhydro-5-[2,4-anhydro-5-azido-3-O-benxyl-5-deoxy-l-ribononamido-(N→5)-2,4-anhydro-5-azido-3-O-benzyl-5-deoxy-l-ribononamido-(N→5)-2,4-anhydro-5-azido-3-O-benzyl-5-deoxy-l-ribononamido-(N→5)]-3-O-benzyl-5-deoxy-l-ribonateC51H58N6O13Ee = 100%[α]D22=-176 (c 0.2, CHCl3)Source of chirality: l-arabinose as starting material

Isopropyl 2,4-anhydro-5-[2,4-anhydro-5-azido-3-O-benxyl-5-deoxy-l-ribononamido-(N→5)-2,4-anhydro-5-azido-3-O-benzyl-5-deoxy-l-ribononamido-(N→5)-2,4-anhydro-5-azido-3-O-benzyl-5-deoxy-l-ribononamido-(N→5)-2,4-anhydro-5-azido-3-O-benzyl-5-deoxy-l-ribononamido-(N→5)-2,4-anhydro-5-azido-3-O-benzyl-5-deoxy-l-ribononamido-(N→5)]-3-O-benzyl-5-deoxy-l-ribonateC75H84N8O19Ee = 100%[α]D23=-158 (c 0.3, CHCl3)Source of chirality: l-arabinose as starting material