15893-06-8Relevant academic research and scientific papers
Stereoselective synthesis of meso-2,6-diaminopimelic acid and its selectively protected derivatives
Gao, Yong,Lane-Bell, Patricia,Vederas, John C.
, p. 2133 - 2143 (2007/10/03)
Four synthetic routes to selectively protected derivatives and isomers of meso-diaminopimelic acid (DAP) (1a), a key constituent of bacterial peptidoglycan, were investigated. N-(tert-butyloxycarbonyl)-D-allylglycine (2) and N-(benzyloxycarbonyl)-L-allylglycine (4) were esterified to ethylene glycol and cyclized via olefin metathesis to a protected derivative 7 of 2,7- diaminosuberic acid. Analogous linking of propane-1,3-diol with 2 and potential precursors of N-(benzyloxycarbonyl)-L-vinylglycine moieties, such as N-(benzyloxycarbonyl)-L-glutamate or N-(benzyloxycarbonyl)-L-methionine sulfoxide, gave 12 or 15, both of which produced the α,β-unsaturated ester 14 upon attempted generation of the vinylglycine precursor for olefin metathesis to DAP derivatives. An alternative route, based on SnCl4- catalyzed ene reaction of methyl N-(benzyloxycarbonyl)-L-allylglycinate (18) with glyoxylate esters of phenylcyclohexanol isomers as chiral auxiliaries, gave ca. 85:15 ratios of diastereomeric alcohols (19 or 20). These could be transformed to DAP derivatives in a series of steps employing azide displacement of corresponding mesylates to introduce the second nitrogen. A third method, involving reduction of pure dimethyl (6S)-2-keto-6-[N- (benzyloxycarbonyl)amino]pimelate (32) to the corresponding alcohol 33 with (S)-binaphthol-ruthenium catalyst as the key step, gives a 79:21 isomeric ratio. The fourth route employs the bis(oxazoline)-copper complex 41 as a chiral catalyst for the ene reaction of methyl (S)-4- (phenylthio)allylglycinate (39) and methyl glyoxylate to afford 42 and 94:6 isometric ratio. Nickel boride removal of sulfur and the double bond in the presence of the Cbz group gives the desired alcohol, dimethyl (2S,6S)-6-[N- (benzyloxycarbonyl)amino]-2-hydroxyheptane-1,7-dioate (33). The required selectively protected second nitrogen is introduced using Mitsunobu inversion with N-tert-butyl [[2-(trimethylsilyl)-ethyl]sulfonyl]carbomate (34) as a key step.
