Metal-coordinating heteroaryl sulfonyl groups, such as the 2-pyridylsulfonyl and the 8-quinolylsulfonyl group, allow the control of the reactivity and stereoselectivity of a great variety of metal-mediated reactions. This concept is rather general and has been applied for the activation of vinyl sulfones and N-sulfonyl imines, as well as in the direct C H functionalization of N-H heterocycles. In particular, this kind of coordinating group has played a key role in the enantioselective Rh-catalyzed addition of boronic acids and Cu-catalyzed reduction of 2-pyridyl vinyl sulfones, the Cu-catalyzed addition of organozinc reagents, and the direct Mannich reaction of glycinate imines to N-heteroarylsulfonyl imines. In addition, a general procedure for the Pd-catalyzed C-2 alkenylation of N-(2-pyridylsulfonyl)indoles and pyrroles has been developed.
E , 7 E ) -N o n a d i e n e d i o a t e s i n A s y m m e t r i c S y n t h e s i sAbstract: A convenient, asymmetric synthesis of (R)-homopipecolic acid methyl ester and an homochiral peptide nucleic acid (PNA) monomer building block are described, starting from the orthogonally disubstituted (2E,7E)-nonadienedioate. The approach involves stereoselective Michael monoaddition of (R)-N-benzyl-Na-methylbenzylamide to the unsaturated ester as the key step, and subsequent transformation of the remaining double bond of the unsaturated acid.Every synthetic route starts from a particular substrate that lends itself to the retrosynthetic scheme planned. The capacity of a substrate to participate in a wide range of synthetic pathways depends on the potential of their structure: cycles, chains and functional groups. Molecules with functional groups that react selectively are attractive from this point of view: the better the chemical orthogonality of the functional groups, the larger the spectrum of synthetic transformations possible and, consequently, the range of accessible targets.Cyclic b-amino acids such as (R)-homopipecolic acid (Scheme 1) have a number of interesting features that have been used to develop synthons of natural products 1 and key intermediates in b-lactam structures. 2 Synthetic oligonucleotides (Scheme 1; DNA/RNA) have been considered as potential gene-targeted therapeutic agents (antisense and antigene). 3 Peptide nucleic acids (PNAs) were first reported in 1991 as DNA mimics 3c and, since this time, a vast number of studies have been reported covering their synthesis, properties and potential applications. Among the known oligonucleotide analogues, acyclic N-(2-aminoethyl)glycyl peptide nucleic acids (Scheme 1; PNA I) or those derived from base-containing d-amino acid derivatives 4 (Scheme 1; PNA II), are found to be very good mimics of DNA/RNA. Within this area, a steadily growing group of analogues in which the sugarphosphate backbone is replaced by a polyamide backbone, is emerging, mainly as a consequence of the intriguing base-pairing properties of their prototype PNA. In this context, we envisaged the synthesis of the amino acid building block mononer 2 in PNA III.We have demonstrated 5 the use of chiral lithium (a-methylbenzyl)benzylamide [(R)-3 or (S)-3] to initiate asymmetric conjugate addition cyclisation of octa-2,6-dienedioate and nona-2,7-dienedioate to generate chiral cyclopentane and cyclohexane derivatives 4 and 5, respectively. 5b-e We have also developed strategies to stereoselectively obtain double-(7) and mono-addition (6, 8, 9 and 10) products 5d (Scheme 2), where the Z-double bond Scheme 1 O base O O P HO O O O base O P O O HO HN N HN N HN O base O base O O DNA/RNA PNA I H(OH) H(OH) PNA I I ; n = 1, m = 3 PNA I I I ; n = 5, m = 1 NH O NH base H N N O O NHBoc EtO 2 C N H CO 2 H (R)-homopipecolic acid O base n m 1 ; n = 1, m = 3 2 ; n = 5, m = 1 n m Downloaded by: Rutgers University. Copyrighted material.
A procedure yielding N ‐benzylidene‐ p ‐toluenesulfinamide ( 1 ) as a white crystalline solid is presented. A one‐necked round‐bottomed flask with a Teflon‐coated magnetic stir bar is connected to a reflux condenser fitted with a calcium sulfate‐filled drying tube. Notes on the paraphernalia and chemicals to be used are provided after the procedure. The chapter concludes with a brief discussion on N ‐Sulfinyl imines 4 as intermediates for the synthesis of a wide range of nitrogen‐containing molecules.
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