Methyl 3,4-0-benzylidene preparation

Preparation of A-(3-methyl-benzylidene)-A - 6-morpholin-4-yl-2-[2-(l-oxy-pyridin-2-yl)-ethoxy]-pyrimidin-4-yl -hydrazine... 

The member of this class which has been studied most thoroughly is 2-benzylidene-4-methyl-5(2 )-oxazolone (57). This compound may be prepared by ring closure of either 3-bromo-2-phenylacetamido-propionic acid or A-(a-halophenylacetyl)alanine (56) [Eq. (30)]. These reactions presumably proceed via unstable halogeno-5(4IT)-oxazolones, which rapidly lose hydrogen halide. 

Tetraazafulvalenes bearing two pyrazole subunits could be prepared by an original way. Tlius, treatment of benzylidene acetophenone with iso-pentylnitrite leads to an A, A -dihydroxy-bipyrazolyl-A, A -oxide, which in turn can be oxidized to TAF of type 100 (72CC961, 79JOC3211). Another type of oxidative dimerization was observed by the reaction of the electron-rich l-methyl-2,4-bis(dimethylamino)imidazole with silver salts (83TL3563). A bis-cation was isolated in 30% yield in the presence of sodium tetrafluo-roborate an unsymmetrical structure 101 was predicted from its NMR data (Scheme 40). 

With the synthesis of the benzylidene hydrazones of selenazoles, it was possible to prepare formazans containing a selenazole ring. Of the compounds already described (Section I,C,1), 2-benzylidene-hydrazino-4,5-diphenyl- and 2-benzylidenehydrazino-4-methyl-5-carb-ethoxy-selenazole were used to couple with diazonium salts in order... 

Two branched-chain sugars, methyl 3-azido-4,6-0-benzylidene-2,3,-dideoxy-3-C-(fluoromethyl)-a-D-flraZ)/ o-hexopyranoside and methyl 2-azido-4,6-0-benzylidene-2,3-dideoxy-2-C-(fluoromethyl)-) -D-r/to-hexo-pyranoside have been prepared through the usual displacement reactions. 

Deoxy-2-[ F]fluoro-3-(9-methyl-D-glucopyranose was prepared by the reaction of methyl 4,6-0-benzylidene-3-0-methyl-2-0-triflyl-) -D-manno-pyranoside (159) with CsH F2, and the possibility of its use as an imaging agent was examined." ... 

Gut, Prins and Reichstein 62 methyl 3-methylthio-4,6-benzylidene-/S-D-idoside (LXX) with a four-fold quantity of Raney nickel (prepared from an eight-fold quantity of alloy) gave methyl 3-desoxy-4,6-benzyli-dene-/S-D-idoside (LXXI) in 92% yield use of a large excess of nickel resulted in simultaneous debenzylidenation. 

After having assembled the D-C precursor the a-(l->3)-attachment of the E unit was to be performed by the NIS method. Therefore a favorable access to the L-olivomycal was needed. We had previously prepared this compound by a five step route from -arabinose ( ). Recently an advantageous preparation of and its epimer Ij-mycaral ( ) by treatment of methyl 2,3-0-benzylidene o-Jj-rhamnopyranoside (35) with methyllithium, was worked out ( ). ... 

The 15-crown-5 and 18-crown-6 derivatives incorporating a methyl 4,6-0-benzylidene-a-D-talopyranoside residue have been de-O-benzylideneated (142) and converted into the biscrown ethers a-o-148 and a-o-149, respectively. Using a similar approach, the triscrown ethers aa-oo-lSO and ace-Do-lSl have been prepared (151) from the 2,3 2, 3 -isomer aa-DD-117 of the bisgalactosido-18-ctown-6 derivative. 

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