C-allyl derivatives

Claisen rearrangement of the allyl enol ether of tnfluoroacetylacetone gives a C-allylated derivative [123] (equation 106)... 

In a similar manner, Jt-allyl complexes of manganese, iron, and molybdenum carbonyls have been obtained from the corresponding metal carbonyl halides [5], In the case of the reaction of dicarbonyl(r 5-cyclopentadienyl)molybdenum bromide with allyl bromide, the c-allyl derivative is obtained in 75% yield in dichloromethane, but the Jt-allyl complex is the sole product (95%), when the reaction is conducted in a watenbenzene two-phase system. Similar solvent effects are observed in the corresponding reaction of the iron compound. As with the cobalt tetracarbonyl anion, it is... 

Allyl ethers of enols and phenols undergo rearrangement to C-allyl derivatives when heated to sufficiently high temperatures. The reaction, named after its discoverer (Claisen, 1912), was first observed when ethyl O-allylacetoacetate was subjected to distillation at atmospheric pressure in the presence of ammonium chloride.1 2... 

Examination of specific carbohydrate-protein interactions can be accomplished with C-glycosides (Scheme 1). A series of C-glucosides and C-mannosides, such as 1, were employed to study the binding differences between mannose and glucose specific lectins (9). C-Mannoside derivatives (3-5) were synthesized from C-allyl derivative 2 and used to block cell-surface lectins thereby inhibiting bacterial adhesion (JO). The primary amine of 4 was functionalized with biotin to target proteins to the bacterial cell surface. 

The 1 -allyl compound (10) and the tricyclic product (11) were shown to arise by independent pathways rather than by sequential migration from the C-allyl derivatives described above. Thus under... 

An interesting approach to symmetrical C-disaccharides was proposed recently by Lowary. 1-0-Acetyl-sugar 97 was converted into 1-C-allyl derivative 97a by classical reaction with allyltrimethylsilane, and this derivative was dimerized under the metathesis conditions with Grubbs catalyst (O Scheme 42) [89]. 

An additional example illustrating the utility of thiophenyl glycosides in free radical mediated C-glycosidations was reported by Waglund, et a/.6 As shown in Scheme 5.2.4, 1-methylcarboxy-l-phenylthioglycosides were treated with allyltributyltin and irradiated with ultraviolet light. The resulting C-allyl derivatives were formed in approximately 30% yields with the stereochemical... 

All allylic derivatives are relatively hepatotoxic and irritant. Allylic alcohol itself serves to create experimental hepatic lesions that allow testing of hepatoprotecting drugs. We consider three categories of allylic derivatives C-allyl derivatives, A-allyl derivatives, and O- and 5-allyl derivatives which often possess alkylating pproperties. 

Analogues 249 (X = H, OH) of UDP-GlcNAc have been prepared as potential inhibitors of chitin synthetases. The synthetic route involved a C-allyl derivative of GlcNAc, which was elaborated by ozonolysis, Wittig reaction and coupling with the nucleoside, followed by hydrogenation or hydroxylation as appropriate. The corresponding amides were also prepared from 5 -amino-5 -deoxyuridine. Lipophilic amino acid methyl esters and methylamides have been coupled to 0-5 of AZT by carbamate links. The products showed anti-HIV activity, but this was not due to carbamate hydrolysis or to direct inhibition of reverse transcriptase, and the mechanism of action may be one not previously observed with nucleoside antivirals. ... 

Since the first report of the rearrangement of allyl ethers of phenols and enols to the corresponding C-allyl derivatives by Claisen [1] in 1912, the mechanistic, stereochemical and synthetic aspects of the reaction have been extensively explored [2]. In modern terminology, the reaction, normally referred to as the Qai-sen rearrangement, is referred to as a [3,3]-sigmatropic rearrangement It has been demonstrated [2] that this reaction, espedaUy the aliphatic version, tolerates various substituents. This fact, coupled with accurate predictability of the stereochemical outcome of the reaction, has resulted in this reaction becoming one of the very important and quite frequently employed methods in the synthesis of complex molecules. 

C. ALLYLIC DERIVATIVES BEARING CHIRAL SULFINATE GROUPS... 

Radical reactions have been further utilised in the construction of branched-chain sugars. Unsaturated iodide (24) with allyltributyltin or Bu3SnH and methyl acrylate has afforded the doubly-branched derivatives (25) and (26) by way of intra- and then inter-molecular radical processes. Similarly, bromide (27) gave the 3-C-allyl derivative (28) which, after transformation into enal (29), underwent a further radical cyclisation (Scheme... 

The acetylated glycosyl chloride of neuraminic acid ethyl ester, with allyltributyltin, gave a- and -C-allyl derivatives which were epoxidized. - C-Hydrotymethylation at C-2 of a related neuraminic acid derivative by carbanionic methods gave the a- and -products in 3 1 ratio. Aminomethyl analogues were also made, but none of these products led to... 

Addition of NBS and pivalic add to the r,2 -unsaturated nucleoside derivative gave the product 31 stereoselectively treatment of 31 with allyl trimethylsilane and tin(IV) chlcHide led to the I -C-allyl derivative 32, and a number of other carbon nucleophiles were similarly introduced. " ... 

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