Synthesis of substituted 8H-benzo[h]pyrano[2,3-f]quinazolin-8-ones via photochemical 6π-electrocyclization of pyrimidines containing an allomaltol fragment

• Constantine V. Milyutin,
• Andrey N. Komogortsev,
• Boris V. Lichitsky,
• Mikhail E. Minyaev and
• Valeriya G. Melekhina

Beilstein J. Org. Chem. 2023, 19, 778–788, doi:10.3762/bjoc.19.58

• as a result of ESIPT-induced reactions (Scheme 1A and B). At the same time, both directions of phototransformation are realized for terarylenes with furan, pyrrole, and oxazolone-bridge fragments (Scheme 1C). However, the suppression of the ESIPT process in such systems makes it possible to perform

A study of the photochemical behavior of terarylenes containing allomaltol and pyrazole fragments

• Constantine V. Milyutin,
• Andrey N. Komogortsev,
• Boris V. Lichitsky and
• Valeriya G. Melekhina

Beilstein J. Org. Chem. 2022, 18, 588–596, doi:10.3762/bjoc.18.61

• processes can be complicated if additional photosensitive fragments are presented in the structure. For example, we previously studied the photochemical behavior of oxazolone terarylenes 9 containing the allomaltol fragment (Scheme 1C) [26]. It has been shown that UV irradiation of such systems leads to a

• obtained results for terarylenes with an oxazolone bridge fragment, we chose pyrazole 16 containing a methoxy group in the allomaltol core as a model object for studying photochemical properties. As it was shown previously for similar oxazolone derivatives [26] the presence of a methoxyl substituent in the

• pyran-4-one substituent, 6π-electrocyclization of 1,3,5-hexatriene system does not occur (Scheme 2). As it was demonstrated earlier [26], UV irradiation of terarylenes containing oxazolone and 3-hydroxypyran-4-one fragments 9 can lead to two types of photoprocesses. Based on the aforementioned results

Synthesis of esters of diaminotruxillic bis-amino acids by Pd-mediated photocycloaddition of analogs of the Kaede protein chromophore

• Esteban P. Urriolabeitia,
• Pablo Sánchez,
• Alexandra Pop,
• Cristian Silvestru,
• Eduardo Laga,
• Ana I. Jiménez and
• Carlos Cativiela

Beilstein J. Org. Chem. 2020, 16, 1111–1123, doi:10.3762/bjoc.16.98

• reaction of 4-((Z)-arylidene)-2-(E)-styryl-5(4H)-oxazolones 2 with Pd(OAc)2 resulted in ortho-palladation and the formation of a dinuclear open-book complexes 3 with carboxylate bridges, where the Pd atom is C^N bonded to the oxazolone. In 3 the two exocyclic C=C bonds of the oxazolone are in a face-to

• ortho-position of the 2,4-aryl rings in the resulting bis-amino acids can be functionalized [30]. Substrates of the (Z)-4-arylidene-2((E)-styryl)-5(4H)-oxazolone type, shown in Figure 2b, are interesting starting materials for the synthesis of new 1,3-diaminotruxillic derivatives. These azlactones are

• that steric hindrance plays a role during the reaction. Oxazolones 2a–j contain two exocyclic C=C bonds in their skeleton and these can, in principle, have different conformations. The NMR characterization of 2a–j showed that they are obtained as single isomers. The oxazolone exocyclic C=C bond has the

Sugar-derived oxazolone pseudotetrapeptide as γ-turn inducer and anion-selective transporter

• Sachin S. Burade,
• Sushil V. Pawar,
• Tanmoy Saha,
• Navanath Kumbhar,
• Amol S. Kotmale,
• Manzoor Ahmad,
• Pinaki Talukdar and
• Dilip D. Dhavale

Beilstein J. Org. Chem. 2019, 15, 2419–2427, doi:10.3762/bjoc.15.234

• and Research, Pune, Pune 411008, India 10.3762/bjoc.15.234 Abstract The intramolecular cyclization of a C-3-tetrasubstituted furanoid sugar amino acid-derived linear tetrapeptide afforded an oxazolone pseudo-peptide with the formation of an oxazole ring at the C-terminus. A conformational study of

• the oxazolone pseudo-peptide showed intramolecular C=O···HN(II) hydrogen bonding in a seven-membered ring leading to a γ-turn conformation. This fact was supported by a solution-state NMR and molecular modeling studies. The oxazolone pseudotetrapeptide was found to be a better Cl−-selective

• transporter for which an anion–anion antiport mechanism was established. Keywords: ion transport; oxazolone; peptidomimetics; pseudo-peptides; sugar amino acid; Introduction Tetrasubstituted α-amino acid (TAA)-derived peptidomimetics offer well-defined turn structures due to the presence of a

Synthesis of nonracemic hydroxyglutamic acids

• Dorota G. Piotrowska,
• Iwona E. Głowacka,
• Andrzej E. Wróblewski and
• Liwia Lubowiecka

Beilstein J. Org. Chem. 2019, 15, 236–255, doi:10.3762/bjoc.15.22

• . Intermediary diacid was first esterified with diazomethane, then the isopropylidene acetal was hydrolyzed, and diester saponification gave N-Boc-protected compound (2S,3R)-35. Via ketopinic acid functionalized 2(3H)-oxazolones When oxazolone 36 derived from (R)-(−)-ketopinic acid was reacted with bromine and

Vinylphosphonium and 2-aminovinylphosphonium salts – preparation and applications in organic synthesis

• Anna Kuźnik,
• Roman Mazurkiewicz and
• Beata Fryczkowska

Beilstein J. Org. Chem. 2017, 13, 2710–2738, doi:10.3762/bjoc.13.269

• reaction with 5-(4H)-oxazolones in the presence of triethylamine formed 4-(2-phosphonioethyl)-5(4H)-oxazolones 116. The oxazolone ring opening with methanol and subsequent deprotonation with sodium methoxide converted phosphonium salt 116 into phosphorous ylide 117, which underwent an intramolecular Wittig

Development of a method for the synthesis of 2,4,5-trisubstituted oxazoles composed of carboxylic acid, amino acid, and boronic acid

• Kohei Yamada,
• Naoto Kamimura and
• Munetaka Kunishima

Beilstein J. Org. Chem. 2017, 13, 1478–1485, doi:10.3762/bjoc.13.146

• synthesis of oxazolone from carboxylic acids and amino acids using a dehydrative condensing reagent, 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMT-MM [19][20][21][22])[23]. Formation of 5-(triazinyloxy)oxazole is also reported to occur when an excess of DMT-MM was used. Recently

• starting materials and relatively more lipophilic activated esters and oxazolone intermediates during the course of the reaction, various 5-(triazinyloxy)oxazoles were uneventfully synthesized under these improved conditions. According to the procedure previously reported [24], we examined Ni-catalyzed

(Thio)urea-mediated synthesis of functionalized six-membered rings with multiple chiral centers

• Giorgos Koutoulogenis,
• Nikolaos Kaplaneris and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2016, 12, 462–495, doi:10.3762/bjoc.12.48

• -oxazolone scaffolds 162 (Scheme 51) [72]. A broad range of both reagents were well tolerated, producing the desired product in moderate to high yields (up to 93%) and diastereoselectivities (up to 99:1 dr) and moderate to good enantioselectivities. Cascade/domino/tandem reactions producing six-membered

Cross-metathesis reaction of α- and β-vinyl C-glycosides with alkenes

• Ivan Šnajdr,
• Kamil Parkan,
• Filip Hessler and
• Martin Kotora

Beilstein J. Org. Chem. 2015, 11, 1392–1397, doi:10.3762/bjoc.11.150

• corresponding vinyl α-C-deoxyriboside α-2 and β-C-deoxyriboside β-2 [16]. As far as further transformation of vinyl C-deoxyribosides relying on the metathesis reaction is concerned, only one paper dealing with successful cross-metathesis with 4-vinyl-5-methyl-2-oxazolone has been reported [16]. This finding is

Total synthesis and cytotoxicity of the marine natural product malevamide D and a photoreactive analog

• Werner Telle,
• Gerhard Kelter,
• Heinz-Herbert Fiebig,
• Peter G. Jones and
• Thomas Lindel

Beilstein J. Org. Chem. 2014, 10, 316–322, doi:10.3762/bjoc.10.29

• 13C NMR signals of oxazole C-5 (10 Hz) and C-4 (6.2 Hz). To the best of our knowledge, this is only the second time that a peptide-derived oxazol-5-ylphosphate has been characterized. Earlier, Boyd and co-workers had converted an oxazolone to an oxazolyl phosphate by treatment with excess diphenyl

• chlorophosphate [14]. In our case, a similar pathway is to be assumed with the oxazolone being formed first. The secondary amine 16 appears to react too slowly to be able to compete with oxazolone formation. Diazirinyl-substituted malevamide D Encouraged by the strong cytotoxicity of 1, we addressed the synthesis

Synthetic scope and DFT analysis of the chiral binap–gold(I) complex-catalyzed 1,3-dipolar cycloaddition of azlactones with alkenes

• María Martín-Rodríguez,
• Luis M. Castelló,
• Carmen Nájera,
• José M. Sansano,
• Olatz Larrañaga,
• Abel de Cózar and
• Fernando P. Cossío

Beilstein J. Org. Chem. 2013, 9, 2422–2433, doi:10.3762/bjoc.9.280

• )-Binap·AuTFA]2. The alanine-derived oxazolone only reacts with tert-butyl acrylate giving anomalous regiochemistry, which is explained and supported by Natural Resonance Theory and Nucleus Independent Chemical Shifts calculations. The origin of the high enantiodiscrimination observed with maleimides and tert

• same solution. Oxazolone derived from glycine 5a was allowed to react with N-phenylmaleimide (NPM) at room temperature (25 °C approx.) using 5 mol % of the chiral catalytic complex and 5 mol % of base (Scheme 1). After completion, a large excess of trimethylsilyldiazomethane was added to obtain the

• oxazolone 5aa and NPM catalyzed by [(Sa)-Binap-AuTFA]2. In previous works, we have demonstrated that the stereoselectivity of the 1,3-DC employing chiral metallic Lewis acids arises from the blockage of one of the prochiral faces [34]. Starting from this selected conformation of the catalyst, our results

Metathesis access to monocyclic iminocyclitol-based therapeutic agents

• Ileana Dragutan,
• Valerian Dragutan,
• Carmen Mitan,
• Hermanus C.M. Vosloo,
• Lionel Delaude and
• Albert Demonceau

Beilstein J. Org. Chem. 2011, 7, 699–716, doi:10.3762/bjoc.7.81

• annulated oxazolone 48, resulted from RCM (2nd-generation Grubbs catalyst) of the imino diene 47 (previously produced by a Pd-catalyzed asymmetric transformation). The following three or five steps, respectively, including the enantioselective dihydroxylation of the RCM product 48, occurred smoothly to

• produce the (+)-DMDP (49) and (−)-bulgecinine (50) (Scheme 8). The starting point in the synthesis of (+)-broussonetine G, 53, was the same annulated oxazolone 48 which, after conversion into the Weinreb amide 51, was coupled with the alkyl bromide substituted spiro compound 52 (Scheme 9). In fact, the