Two synthetic photoactive azidoarylphosphatidylcholines were used to investigate the level of interaction between D-~-hydroxybutyrate apodehydrogenase (apoBDH), an amphipathic membrane protein. with the hydrophobic domain of phosphoiipjds. The two synthetic lecithins, PL I (1-myristoyl-2-12-N-(4-azido-2-nitrophenyl)aminododecanoyl-sn-glycero-3-phosphocholine) and PL II (I-myristoyl-2-(2-azrdo-4-nitrobenzoyl)-sn-glycero-3-phosphocholine), are able to reactivate the non-active purified apoBDH as well as the non-photoactive homologs, indicating that the photoreactive chemical groups are without effect on the cofactor properties of phosphatidylcholine. Photoirradiation of reconstituted complexes between phospholipid containing ~idoaryllecithin and apoBDH leads to a covalent binding of some synthetic lecithin molecules on the protein. The labelling, about 3 times higher with PL II than with PL I, suggests that the area of interacting domain of BDH with the hydrophobic moiety of phospholipid IS more important at or near the surface of the lipid bilayer than in the inner part. This approach is further demonstration that BDH is an integral protein.
D-&Hydro.rybutyrate apodehydrogenase
A procedure has been developed which permits the synthesis of mixed-acid 1.2-di-O-aroyl-sn-glycerols via 1.6-di-0-aroyl-2.5-di-O-tosyl-D-mannitol. The method was applied to the synthesis of some (S) -( +)-l-O-aroyl-2-Otosyl-sn-glycerols. In order to check the structure and the optical purity of the 1.2-diglycerides, tritylation to give 3-trityl ethers was carried out. 1 -Trityl ethers were prepared by a second method via 3-O-aroyl-sn-glycerols. The optical rotations of the 3-and 1 -trityl ethers were compared. Oxidation of 1,6-di-O-aroyl-2,5-di-O-tosyl-omannitol a t temperatures above 25 "C took place with complete or partial racemisation.IN connection with previous studies,1*2 chiral mixed diglycerides t were required as intermediates in the synthesis of di-O-aroyl-sn-glycerol 2-or 3-iodohydrins. This paper describes a new preparation of l-O-aroyl-2-0tosyl-sn-glycerols, and the measurement of the optical tri-0-isopropylidene-D-mannitol (1 1) into 3,4-O-isopropylidene-D-mannitol (12) was by the method of Wigging~.~ Condensation with benzoyl chloride gave 1,6-di-0-benzoyl-3,4-O-isopropylidene-~-mann~tol (13). This compound is identical with product (2) [analytical and spectroscopic data (n.m.r. and i.r.)]. This confirms that the 3,4-isopropylidene derivative was isolated. Moreover, hydrolysis of (13) with hydrochloric acid gave
. Can. J. Chem. 70, 2319 (1992). Precursors of phospholipids or ether lipids were synthesized from ~-m a n n i t~l , i.e., 1-0-myristoyl-2-0-benzyl-sn-glycerol 11 and 1-0-hexadecyl-2-0-benzyl-sn-glycerol 13. The chemical pathways involved sequential protection reactions using allyl, triphenylmethyl, or benzyl groups via 3-0-allyl-sn-glycerol. Eleven intermediates were isolated and for the first time characterized with their spectrometric (especially 'H nmr) and physical parameters and yield. This work allowed preparation of chemically defined membrane phospholipids from compound 11 as well as ether lipids from compound 13 with cell mediator activities bearing different probes such as photoactivatable, fluorescent, or radioactive groups.
The reaction of ethyl diazoacetate with the N-ethoxycarbonyl-N-(2,2,2-trichloroethylidene)amine yields, by a nucleophilic addition, a new diazo compound that gives 1,3-dipolar cycloaddition reactions with acetylenic esters and maleimides. With acetylenic esters, the cycloadduct leads to substituted pyrazoles by [1,5] sigmatropic rearrangements. With maleimides, we observe a diastereospecific cycloaddition reaction. The intermediary cycloadduct evolves by nitrogen elimination to give a maleimidocyclopropane. The diastereospecificity was explained by an endo-anti approach of the reactants. Keywords: N-ethoxycarbonyl-N-(2,2,2-trichloroethylidene)amine, ethyl diazoacetate, nucleophilic addition, 1,3-dipolar cycloaddition, sigmatropic rearrangement, diastereoselectivity.
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