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A diversity-oriented protocol has been developed for the assembly of densely hydroxylated cycloheptane amino acids via succession of a vinylogous Mukaiyama aldol reaction (VMAR), a Morita-Baylis-Hillman reaction (MBHR), and an intramolecular pinacol coupling reaction (IPCR). The plan utilizes D- or L-configured glyceraldehyde derivatives as ‘chirar’ surrogates of glyoxal and N-[(tert-butoxycarbonyl)-2-(tert-butyldimethylsilyl)oxy]pyrrole as the synthetic equivalent of the α,γ-dianion of γ-aminobutanoic acid. The parallel, asymmetric syntheses of four cycloheptane representatives proceed with high diastereocontrol and virtually complete enantioselectivity in ten steps and overall yields of 15–37%. [ABSTRACT FROM AUTHOR]

The enantioselective synthesis of cyclopentanedicarboxylic amino acid 1, a novel rigid and functionalized L-glutamic acid analogue, has been achieved in 15 linear steps from silyloxypyrrole 3, utilizing L-glyceraldehyde 4 as the source of chirality. The key steps in the synthesis are three sequential aldol-based carbon-carbon bond-forming reactions: two crossed vinylogous aldol additions (2 + 3 → 8 and 4 + 5 → 10 + 11) and one intramolecular silylative aldolization (6 → 7). En passant, the short syntheses of (2S)2-hydroxymethylglutamic acid (16) and its (2R)-enantiomer ent-16, a potent metabotropic glutamate receptor agonist, have been achieved. [ABSTRACT FROM AUTHOR]