Tris methyl bromide, synthesis

The C20 amino acid (2.V,3.S, 8.S, 9.S, 4/ , 6 )-3-amino-9-methoxy-2,6,8-tri-methyl-10-phenyldeca-4,6-dienoic acid (Adda 19) is a molecule of interest to biologists and organic chemists as a component of the hepatotoxic cyclic peptides called microcystins. Kim and Toogood used Ireland-Claisen rearrangement in their successful synthesis of Adda8 (Scheme 1.3h). The ester 20 underwent highly diastereoselective Ireland-Claisen rearrangement to provide the acid 21. Conversion of this acid to the phosphonium bromide 22 was achieved in nine... 

Synthesis of Tris(trimethylsilyl)methyl Bromide. Tris-(trimethylsilyl)methyl bromide (trisyl bromide) can be prepared in 75% yield by photochemical bromination of neat tris(trimethylsilyl)methane at 180-190 °C in less than 5 h (eq 1). 

Compound 33 also lends itself to the synthesis of 1,5-linked disaccharides. Thus, its condensation180 with 2,3,4,6-tetra-O-acetyl-a-D-glucopyranosyl bromide, and with methyl 2,3,4-tri-O-acetyl-a-D-glucopyranosyluronate bromide, respectively, yields the corresponding /3-D-linked disaccharides (97 and 98). 

Methyl 2,3-di-0-benzyl-oc-D-glucopyranoside gives 58% of 2,3,6- and 21% of 2,3,4-tri-0-benzyl ether on reaction with 1.4 equiv. of sodium hydride and benzyl bromide [71]. In a remarkably selective reaction, 62% of methyl 2,4,6-tri-0-benzyl-a-D-glucopyranoside result from the unprotected methyl a-D-glucopyranoside [74]. Benzyl chloride has been used for this transformation, as well as for the efficient synthesis of methyl 2,4-di-0-benzyl-a-D-xylopyranoside [75] 1 As expected, OH-2 in methyl 4,6-0-benzylidene-a-D-glucopyranoside is more reactive [71] than OH-3. 

The D-<2/ <2 z o-hex-2-ulopyranosonates have been used as building blocks for the synthesis of spiroheterocyclic carbohydrates.276,277 The glycosyl donor, methyl (3,4,5-tri-O-acetyl-/J-D- rafo 0-hex-2-ulopyranosyl)onate bromide (102), obtained from the methyl ester of D-uraftinn-2-hexulosonic acid may be converted into its nitrophenyl a-glycoside, which in turn is reductively cyclized to the spirane 103 (Scheme 8). 

A facile, one-pot synthesis of an alkylated tetrahydrofuranone intermediate was applied to the synthesis of a novel hexahydrofuro[3,4-6]furan derivative <83TL2335>. Reaction of methyl acrylate with methyl sodium benzilate in DMSO gave the intermediate 3-oxo ester carbanion, which was alkylated with allyl bromide to yield the tetrahydrofuranone derivative (408). Subsequent hydrolysis and decarboxylation of (408), followed by reduction with lithium tri-r-butoxyaluminum hydride gave compound (409), which with excess iodine and Na2C03 afforded an 85 15 mixture of the epimers (410a) and (410b) in 95% yield (Scheme 38). 

The constitution and configuration of cellobiose was confirmed by synthesizing the sugar, though in very small yield. This was the first synthesis of cellobiose by way of a trityl compound. Methyl 2,3,6-tri-acetyl-/S-D-glucopyranoside (XXVII) was condensed with tetraacetyl-D-glucopyranosyl bromide and the condensation product identified as methyl heptaacetyl-(8-cellobioside (XXVIII). Since the latter compound yields acetobromocellobiose (heptaacetylcellobiosyl bromide) and cello-... 

The synthesis of caoutchouc from other compounds than the ter-penes themselves was made possible by two syntheses of isoprene which established its constitution. These syntheses were by Ipatiew and Euler in 1897-98. The synthesis of Ipatiew was from di-methyl tri-methylene di-bromide or di-brom iso-pentane which is 2-methyl 2-4-di-brom butane. The reactions are as follows two products being obtained one of which is isoprene ... 

---