Synthesis of carbocyclic analogues of lipid X

Synthesis and Conformational and Biological Aspects of Carbasugars

“…Cleavage of the allyl group, acylation at 3-OH by (R)-3-benzoyloxytetradecanoic acid, and catalytic hydrogenation, to remove the benzyl and benzylidene groups, yielded the carbasugar analogue of Lipid X (1073). 391 Lewis and co-workers followed the synthetic sequence developed by Quiclet-Sire and co-workers for the preparation of glucosamine derivative 1055 and reported two different routes to the carbasugar analogue of Lipid X (1073) (Schemes 170 and 171). 392 The two sequences employed different protecting groups on the ester side chains.…”

“…Carbamate 1055 was also used in the preparation of carbasugar analogues of N -acetylmuramyl- l -alanyl- d -isoglutamine (MDP, 1068 ) and Lipid X (Scheme ). Carbamate 1055 was hydrogenolyzed to give a triol which was protected as a benzylidene derivative and etherified with ( S )-α-chloropropionic acid to yield acid 1064 , which was condensed with l -Ala- d -isoglutamine benzyl ester ( 1065 ) to give 1066 .…”

“…Cleavage of the oxazolidinone ring followed by N -acylation with N -( R )-3-benzyloxytetradecanoyloxysuccinimide and 4,6- O -benzylidenation furnished 1071 , which was converted to dibenzylphosphono derivative 1072 . Cleavage of the allyl group, acylation at 3-OH by ( R )-3-benzoyloxytetradecanoic acid, and catalytic hydrogenation, to remove the benzyl and benzylidene groups, yielded the carbasugar analogue of Lipid X ( 1073 ) 169 Synthesis of Carbasugar Lipid X ( 1073 ) a a Reagents: (i) Li, liq NH 3 , THF, −78 °C; (ii) PhCHO, TsOH, DMF, 54%, two steps; (iii) NaH, allyl bromide, DMF, 71%; (iv) AcOH, H 2 O, 95%; (v) LiOH, MeOH−H 2 O, 93%; (vi) ( R )-3-benzyloxytetradecanoylsuccinimide, DMF, 78%; (vii) ZnCl 2 , PhCHO, 86%; (viii) N , N -ethyldiisopropyldibenzylphosphoramidite, tetrazole, CH 3 CN, 73%; (ix) SeO 2 , dioxane, AcOH, 100 °C, 62%; (x) ( R )-3-benzyloxytetradecanoic acid, DMAP, DCC, CH 2 Cl 2 , 52%; (xi) H 2 , Pd/C, THF, H 2 O, 85%. …”

Synthesis of Arylglycines from CO2 through α-Amino Organomanganese Species

“…With these precedents in mind, we envisioned a new strategy for α-amino acid synthesis using N -acyl -N,O -acetals, which are easily prepared from the corresponding aldehydes or acetals (Scheme , eq 2). , These N , O -acetals would be converted into iminium species in the presence of a Lewis acid. The following reduction of the resulting iminium species by a zerovalent metal would occur to produce α-amino metals, − which would undergo carboxylation with CO 2 followed by protonation to afford the target amino acids.…”