Lactone moiety

The results obtained showed that carbon, oxygen, or nitrogen functionalities are readily introduced into the a,p positions of the lactone moiety. In this way, useful precursors for natural product synthesis are accessible (88TL5317). 

CotLespondingly, tlie catalytic 1,4-addition of dialkylzinc reagents to 3-nitro-iimarin 89 iSdieme 7.24), witli a fixed irans orientation of tlie aiyl and nitro oiips, proceeds witli excellent yidds 190-99 96), bigli diastereoselectivity Id.r. up to ), and enantiosdectivities of up to 9296. Hydrolysis of tlie lactone moiety in 90 IS accompanied by decarboxylation, providing an asymmetric syntliesis of /J-aiyl-troalkane 91. 

Calein A (24) which contains one a, 0-unsaturated ketone, ester and lactone moiety has only minor effects on most seed germinations but strongly inhibits Palmer amaranth (75%) at the 0.05 mM level. 

The described approach also allows a simple access to indole alkaloids of the vallesiachotamine type. In this process, the Cbz-protected secondary amino function in the formed cycloadducts such as ent-2-805 is deprotected by hydrogenolysis. There follows an attack at the lactone moiety to form a lactam. In this way, the indole alkaloid (-)-dihydroantirhin (2-797) was prepared [400, 401]. 

The diversity of the Ugi-MCR mainly arises from the large number of available acids and amines, which can be used in this transformation. A special case is the reaction of an aldehyde 9-26 and an isocyanide 9-28 with an a-amino acid 9-25 in a nucleophilic solvent HX 9-30 (Scheme 9.5). Again, initially an iminium ion 9-27 is formed, which leads to the a-adduct 9-29. This does not undergo a rearrangement as usual, but the solvent HX 9-30 attacks the lactone moiety. Such a process can be used for the synthesis of aminodicarboxylic acid derivatives such as 9-31 [3, 30],... 

The synthesis of the D-gulonolactam 36 was based on an intramolecular cyclisation /ring enlargement strategy involving reduction of the azido group in 35 followed by intramolecular nucleophilic attack on the lactone moiety to afford 36 in excellent yield <06T7455>. 

The study of Fuji et al. shows that the addition of lithium enolate 75 to ni-troamine 74 is readily reversible quenching conditions are thus essential for getting a good yield of product 76. An equilibrium mixture of the adducts exists in the reaction mixture, and the elimination of either the prolinol or lactone moiety can take place depending on the workup condition (Scheme 2-34). A feature of this asymmetric synthesis is the direct one pot formation of the enantiomer with a high ee value. One application of this reaction is the asymmetric synthesis of a key intermediate for indole type Aspidosperma and Hun-teria alkaloids.68 Fuji69 has reviewed the asymmetric creation of quaternary carbon atoms. 

Hg/mL) while its lactone analogue spirafolide (IC, = 4 pg/mL) showed the highest activity. It should be considered that the lack of lactone moiety caused a decrease in the potential cytotoxic activity of the compound. 

Maddrell, S.J., Turner, N.J., Kerridge, A., Willetts, A.J. and Crosby, J., Nitrile hydratase enzymes in organic synthesis enantioselective s3mthesis of the lactone moiety of the mevinic... 

Correspondingly, the catalytic 1,4-addition of dialkylzinc reagents to 3-nitro-coumarin 89 (Scheme 7.24), with a fixed trans orientation of the aryl and nitro groups, proceeds with excellent yields (90-99%), high diastereoselectivity (d.r. up to 20 1), and enantioselectivities of up to 92%. Hydrolysis of the lactone moiety in 90 was accompanied by decarboxylation, providing an asymmetric synthesis of 8-aryl-nitroalkane 91. 

The strategy was chosen because compound 57 is readily prepared from 58 and is easily transformed to 56 by a-alkylation followed by reduction of the lactone moiety. Additionally, both cis- and frans-lactone lignans can be synthesized by one common intermediate. 

Cyclic peptides are important biologically active compounds that combine peptide properties with conformational bias and often improved serum stability and membrane penetration [1-3]. Depsipeptides are similar compounds, but they contain as part of their backbone one or more hydroxylated amino acid residues that add ester or lactone moieties to the peptide (Fig. 1) [4-6]. Cyclo- and... 

In 1998, Ito et al. isolated clausamine-A (217), -B (218), and -C (219), each in their racemic form from the branches of C. anisata (173). The clausamines have a 1-oxygenated carbazole framework with an annulated six-membered lactone in the 3,4-position. They represented the first examples of naturally occurring carbazole alkaloids with a lactone moiety (173). Later in the same year, Wu et al. reported four further carbazolelactone alkaloids, clausevatine-D (220), -E (221), -E (222), and -G (223), from the root bark of C. excavata (Rutaceae) (174). This plan is a wild shrub... 

A large group of the lignane-type natural products characteristically contain a substituted y-lactone moiety. During attempts to synthesize these natural products the diastereoselective a-alkylation of a y-lactone was a central step in each of the chosen routes. 

Ll.1.3.2.2.3.1. Six-Membered Heterocyclic Compounds with a Lactone Moiety... 

Halicholactone 214, a marine metabolite with lipoxygenase inhibitory activity, belongs to the family of oxylipins which all contain a lactone moiety substituted by a /ra r-disubstituted cyclopropane subunit. Stereoselective RCM for the formation of the nine-membered lactone core in 214 was the penultimate step (212 —> 213) in a asymmetric... 

In order to replace the chlorine atom by the desired hydroxy functionality, di-isobutylaluminum hydride (DIBAL-H) reduction followed by an acid-catalyzed acetalization with isopropanol in refluxing benzene had to be performed to protect the lactone moiety as an acetal and provided the thermodynamically preferred a-anomer 38 together with 5-8% of the other epimer. The conversion of the... 

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