The synthesis of homochiral homo-oligomers of cis- and trans-3-aminotetrahydrofuran-2-carboxylic acids (parent cis- and trans-furanoid-β-amino acids, referred to as "cis-/trans-FAA") has been carried out to understand their secondary structures and their dependence on the ring heteroatom. The oligomers of two diastereomers have been shown to have a distinct left-handed helicity. The cis-FAA homo-oligomers show a 14-helix structure, in contrast to the homo-oligomers of cis-ACPC, which adopt a sheet like structure. The trans-FAA homo-oligomers were found to adopt a 12-helix structure, the same trend found in trans-ACPC homo-oligomers. With the help of ab initio calculations, the structural features of cis-ACPC and cis-FAA hexamers were compared. We believe that the more compact packing of the cis-FAA hexapeptide should be due to a more favorable interaction between the ring and the backbone amide hydrogen.
The first enantiospecific synthesis of (-)-parvifoline, employing ring-closing metathesis as the key step, and (-)-curcuquinone from naturally occurring (R)-(+)-citronellal is described.
The total synthesis of (−)-lentiginosine, epi-1,2-lentiginosine and dihydroxypyrrolizidine is reported from an aldehyde as a starting material using organocatalysis and asymmetric dihydroxylation as key steps.
Herein we describe the synthesis of cis‐/trans‐3‐aminotetrahydrofuran‐2‐carboxylic acids (cis‐/trans‐FAA) having a γ‐methoxy group cis to the amine. The homo‐oligomers of these two diastereomeric FAAs have been prepared. Preliminary investigation of their solution secondary structures revealed that they are the same as the homo‐oligomers of the parent cis‐/trans‐FAA with the methoxy group only being a spectator substituent.
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