Synthesis regiospeciflcity

The regiospeciflc ortholithiation of 3H-naphtho[2,l-fe]pyrans has also been used to advantage in methylteretifolione B synthesis. ... 

A novel ring-contraction reaction which proceeds via an epi-sulfonium ion intermediate has been reported for the simple and regiospeciflc synthesis of mono-and symmetrically di-functionalized tetrathiamacrocycles, starting with the mono- or dichloro-substituted macrocycles that have one or two more ring atoms. 

Based on the observation that 1,4-dimethoxycyclohexadiene cationic iron complex 310 undergoes regiospeciflc nucleophilic addition at C(l) and not at C(S) Stephenson et al [81] developed a new formal synthesis of ( )-lycoramine (300) (Scheme 47). Thus, the arylcarbanion 311, derived from the bromocompound 312 by halogen-metal exchange, reacted with 310 to provide the ipso addition product 313. Oxidative elimination of the C(l) methoxyl group generated the salt 314. 

Hess, E., Sichler, S., Kluge, A. and Coenen, H. H. (2002) Synthesis of 2-[18F]fluoro-L-tyrosine via regiospeciflc fluoro-de-stannylation. Appl. Rad. Isot., 57, 185-191. 

A. Kiener, J.-P. Roduit, A. Tschech, A. Tin-schert, K. Heinzmann, Regiospeciflc enzymatic hydroxylations of pyrazinecarboxylic acid and a practical synthesis of 5-chlor-opyrazine-2-carboxylic acid, Synlett 1994, 10, 814-816. 

The butterfly pheromone (18) was previously prepared by the oxidation of the necine base supinidine (17) (Scheme 4). A simple synthesis of this pheromone has now been reported by Pizzorno and Albonico. Regiospeciflc 1,3-cycloaddition of propargylic aldehyde with the postulated azomethine ylide intermediate (19), formed by refluxing N-formylproline in acetic anhydride with 2,6-di-t-butyl-4-methylphenol as anti-oxidant, gave a 40% yield of the dihy-dropyrrolizine (18). 

Grigg, R., Santhakumar, V., Sridharan, V. et al. (1991) The synthesis of bridged-ring carbo-and hetero-cycles via palladium catalysed regiospeciflc cyclisation reactions. Tetrahedron, 47, 9703-20. 

The process whereby a /3-keto-ester is converted into an a, -unsaturated ester via an enolphosphate has been applied to the synthesis of isoprenoid natural products (Scheme 48),and in a regiospeciflc synthesis of 6-deoxy-anthracycline intermediates. 

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