Synthesis of complex intermediates for the study of a dehydratase from borrelidin biosynthesis

• Frank Hahn,
• Nadine Kandziora,
• Steffen Friedrich and
• Peter F. Leadlay

Beilstein J. Org. Chem. 2014, 10, 634–640, doi:10.3762/bjoc.10.55

• target molecules were obtained from a common precursor aldehyde in the form of N-acetylcysteamine (SNAc) thioesters and methyl esters in 13 to 15 steps. Key steps for the assembly of the polyketide backbone of the dehydratase substrate analogue were a Yamamoto asymmetric carbocyclisation and a Sakurai

• polyketide-derived thioesters suited for biosynthesis studies. Keywords: aldol reaction; coenzyme A; natural products; pig liver esterase; polyketide biosynthesis; protection groups; Introduction Borrelidin (1) is a macrolactone polyketide natural product with promising antibacterial, antimalarial

• recognition of this prosthetic group is essential for proper substrate orientation in the active site and catalysis with natural stereoselectivity [13]. To mimic the ACP-bound state of PKS intermediates, their analogues, free SNAc thioesters, are used in enzyme assays. Alternatively, ACP-bound substrates can

Intermediates in monensin biosynthesis: A late step in biosynthesis of the polyether ionophore monensin is crucial for the integrity of cation binding

• Wolfgang Hüttel,
• Jonathan B. Spencer and
• Peter F. Leadlay

Beilstein J. Org. Chem. 2014, 10, 361–368, doi:10.3762/bjoc.10.34

• of the ACPX-thioesters of these compounds and a detailed study of the final steps of monensin biosynthesis using authentic substrates and recombinant MonD, MonE and MonCII [40][41]. Experimental Construction of deletion strains: For generation of the deletion mutants ΔmonE, ΔmonD and ΔmonDΔmonE of

Use of 3-[¹⁸F]fluoropropanesulfonyl chloride as a prosthetic agent for the radiolabelling of amines: Investigation of precursor molecules, labelling conditions and enzymatic stability of the corresponding sulfonamides

• Reik Löser,
• Steffen Fischer,
• Achim Hiller,
• Martin Köckerling,
• Uta Funke,
• Aurélie Maisonial,
• Peter Brust and
• Jörg Steinbach

Beilstein J. Org. Chem. 2013, 9, 1002–1011, doi:10.3762/bjoc.9.115

• chlorides can be generated by oxidation with aqueous chlorine from a variety of organosulfur species such as thiols, sulfides, disulfides, thioesters, isothiouronium salts, xanthates and thiocyanates [22]. The latter class of organic sulfur compounds seems to be most advantageous, as organic thiocyanates

Isotopically labeled sulfur compounds and synthetic selenium and tellurium analogues to study sulfur metabolism in marine bacteria

• Nelson L. Brock,
• Christian A. Citron,
• Claudia Zell,
• Martine Berger,
• Irene Wagner-Döbler,
• Jörn Petersen,
• Thorsten Brinkhoff,
• Meinhard Simon and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2013, 9, 942–950, doi:10.3762/bjoc.9.108

• ]. This is reflected by their volatile bouquets that are dominated by sulfur compounds such as polysulfides 1 and 2 (Figure 1), thiosulfonates 3, thioesters 4, or sulfones 5, and phenylacetate-derived volatiles such as the moderately antibacterial compounds tropone (6) and tropone hydrate 7 [3][4][5][6

Quantification of N-acetylcysteamine activated methylmalonate incorporation into polyketide biosynthesis

• Stephan Klopries,
• Uschi Sundermann and
• Frank Schulz

Beilstein J. Org. Chem. 2013, 9, 664–674, doi:10.3762/bjoc.9.75

• Polyketides are biosynthesized through consecutive decarboxylative Claisen condensations between a carboxylic acid and differently substituted malonic acid thioesters, both tethered to the giant polyketide synthase enzymes. Individual malonic acid derivatives are typically required to be activated as coenzyme

• A-thioesters prior to their enzyme-catalyzed transfer onto the polyketide synthase. Control over the selection of malonic acid building blocks promises great potential for the experimental alteration of polyketide structure and bioactivity. One requirement for this endeavor is the supplementation of

• mutated PKS. Another option is the exogenous supply of the malonate derivative [28], typically activated as N-acetylcysteamine thioesters (malonyl-SNAC) [29][30][31][32][33][34][35][36][37][38][39][40]. Despite its apparent simplicity, the latter option is not well characterized for in vivo applications

Efficient Cu-catalyzed base-free C–S coupling under conventional and microwave heating. A simple access to S-heterocycles and sulfides

• Silvia M. Soria-Castro and
• Alicia B. Peñéñory

Beilstein J. Org. Chem. 2013, 9, 467–475, doi:10.3762/bjoc.9.50

• diverse heterocycles containing sulfur atoms by intra- [42][43][44] and intermolecular [45][46][47] reactions. Aryl thioesters are versatile intermediates for the synthesis of a variety of sulfur compounds including aryl thiols, aryl alkyl sulfides, aryl sulfenyl chlorides, aryl sulfonyl chlorides [48

Thioester derivatives of the natural product psammaplin A as potent histone deacetylase inhibitors

• Matthias G. J. Baud,
• Thomas Leiser,
• Vanessa Petrucci,
• Mekala Gunaratnam,
• Stephen Neidle,
• Franz-Josef Meyer-Almes and
• Matthew J. Fuchter

Beilstein J. Org. Chem. 2013, 9, 81–88, doi:10.3762/bjoc.9.11

• . In support of this approach, Miyata and co-workers synthesised a number of SAHA-derived thioesters during their research of nonhydroxamate inhibitors of HDACs, which exhibited moderate to high potency in enzymatic and cell-based assays [24][25]. Interestingly, the potencies of their compounds were

• could be improved with further refinement of the reaction conditions [28]. Thioesters 7–9 were assayed against A549, MCF7 and WI38 cell lines, in addition to recombinant human rHDAC1 (class I) and recombinant human HDAC6 (rHDAC6, class II) as previously reported [20]. Psammaplin A (3), prereduced

• psammaplin A thiol (4), and SAHA (1) were included as control compounds. The results are shown in Table 1. IC506/1 is defined by the ratio IC50HDAC6/IC50HDAC1 and was used as an indicator of isoform selectivity in vitro. The synthesised thioesters displayed modest but significant cytotoxic activity in our

Peptoids and polyamines going sweet: Modular synthesis of glycosylated peptoids and polyamines using click chemistry

• Daniel Fürniss,
• Timo Mack,
• Frank Hahn,
• Sidonie B. L. Vollrath,
• Katarzyna Koroniak,
• Ute Schepers and
• Stefan Bräse

Beilstein J. Org. Chem. 2013, 9, 56–63, doi:10.3762/bjoc.9.7

• attachment to other molecules through a variety of functional groups, such as amines (–NH2) and carboxylic acids (–COOH) resulting in peptide bonds, thiols (–SH) resulting in disulfides, thioethers or thioesters, aldehydes (–CHO) and hydroxy (–OH) groups. Nonetheless, coupling to these groups often requires

Imidazolinium and amidinium salts as Lewis acid organocatalysts

• Oksana Sereda,
• Nicole Clemens,
• Tatjana Heckel and
• René Wilhelm

Beilstein J. Org. Chem. 2012, 8, 1798–1803, doi:10.3762/bjoc.8.205

• and amidinium salts as soft Lewis acid organocatalysts is described. These salts were suitable catalysts for the activation of unsaturated thioesters in a Diels–Alder reaction and in the ring opening of thiiranes and epoxides. The products were isolated in good yields. The mild catalysts did not cause

• desulfurization of the products containing a thiol or thiocarbonyl group. Keywords: Diels–Alder; ionic liquids; organocatalysis; soft Lewis acids; thiiranes; thioesters; Introduction Salts with melting points below 100 °C are known as ionic liquids and are often used as novel solvents for reactions and

Asymmetric organocatalytic decarboxylative Mannich reaction using β-keto acids: A new protocol for the synthesis of chiral β-amino ketones

• Chunhui Jiang,
• Fangrui Zhong and
• Yixin Lu

Beilstein J. Org. Chem. 2012, 8, 1279–1283, doi:10.3762/bjoc.8.144

• unsatisfactory and the enantioselectivities were modest [20]. In recent years, inspired by the enzymatic synthesis of polyketides and fatty acids in biological systems, the enantioselective decarboxylative reactions of malonic acid half thioesters (MAHTs) have received much attention. In this regard, various

• alternative decarboxylation–addition pathway at this stage. In fact, in sharp contrast to the popular use of malonic acid half thioesters (MAHTs) as an ester enolate equivalent in enantioselective decarboxylative additions [39], the employment of β-keto acids as a reaction partner in decarboxylative processes

Building photoswitchable 3,4'-AMPB peptides: Probing chemical ligation methods with reducible azobenzene thioesters

• Gehad Zeyat and
• Karola Rück-Braun

Beilstein J. Org. Chem. 2012, 8, 890–896, doi:10.3762/bjoc.8.101

• thioesters 1b and 2b instead of a C-terminal thioester peptide. We explored the conventional cysteine-based NCL with Cys-peptide 3, and also screened the application of the TFA-cleavable 4,5,6-trimethoxy-2-mercaptobenzyl (Tmb) and 1-(2,4-dimethoxyphenyl)-2-mercaptoethyl auxiliaries by using peptides 4 and 5

• synthesis and evaluation of photoswitchable protein analogues, for example receptors with the photoswitch placed in the direct neighborhood of the specific C-terminal binding motif. Results and Discussion The azobenzene ω-amino-acid thioesters 1b and 2b were prepared by following and applying literature

• reactions were conducted under normal lighting conditions, and therefore small amounts of the cis-azobenzene forms of the thioesters 1b/2b and of the ligation products 10–15 were detected during HPLC monitoring (Supporting Information File 1). The results of all ligation courses prior to purification by

Aromatic and heterocyclic perfluoroalkyl sulfides. Methods of preparation

• Vladimir N. Boiko

Beilstein J. Org. Chem. 2010, 6, 880–921, doi:10.3762/bjoc.6.88

• . However, in the presence of C6F13I the reaction follows a different course where the perfluorinated radical attacks sulfur with the formation of the fluorinated sulfide [217] (Scheme 57). The irradiation of thioesters of trifluoroacetic and trifluoromethanesulfonic acids in refluxing methylene chloride

• results in their decarbonylation (or desulfonation in the case of CF3SO2SR) with the production of CF3• radicals, which then react with diaryl- or dialkyl disulfides (Scheme 58). The formation of aryl trifluoromethyl sulfides from thioesters of trifluoroacetic acid occurs in rather better yields (30–40

• %) than from the corresponding esters of trifluoromethanesulfonic acid (20–30%). Alkyl thioesters of trifluoroacetic and trifluoromethanesulfonic acids form AlkSCF3 in higher yields (up to 80%). As shown in Scheme 58, the CF3• radical can attack at several sites. Phenyl selenide esters of