Hierarchically assembled helicates as reaction platform – from stoichiometric Diels–Alder reactions to enamine catalysis

• David Van Craen,
• Jenny Begall,
• Johannes Großkurth,
• Leonard Himmel,
• Oliver Linnenberg,
• Elisabeth Isaak and
• Markus Albrecht

Beilstein J. Org. Chem. 2020, 16, 2338–2345, doi:10.3762/bjoc.16.195

• the amino alcohols 10a–d were protected with a Boc group [42][43]. Esterification of the protected alcohols 11a–d [33][44] with 2,3-dioxosulfinylbenzoyl chloride obtained from 2,3-dihydroxybenzoic acid and thionyl chloride afforded the N-Boc-substituted catechol ligands 12a–d [33][36]. They were

Synthetic approaches to bowl-shaped π-conjugated sumanene and its congeners

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 2212–2259, doi:10.3762/bjoc.16.186

• common organic solvents, they first tried the esterification reaction with soluble monoiodosumanene 79 using Pd(OAc)2 under CO atmosphere and obtained the desired sumanene methyl ester in very low yield. Surprisingly, when they used hexabromosumanene 94 under similar reaction conditions, no product

• formation was observed. Therefore, they used a Pd-catalyzed carbonylative esterification in the presence of phenyl formate which in situ generated CO and phenol to provide the required product 97 in 73% yield (Scheme 24). In an independent work reported in 2017, Fukushima and co-workers detailed the

Azo-dimethylaminopyridine-functionalized Ni(II)-porphyrin as a photoswitchable nucleophilic catalyst

• Jannis Ludwig,
• Julian Helberg,
• Hendrik Zipse and
• Rainer Herges

Beilstein J. Org. Chem. 2020, 16, 2119–2126, doi:10.3762/bjoc.16.179

• study is 4-(N,N-dimethylamino)pyridine derivative 1 (Figure 1). The parent 4-(N,N-dimethylamino)pyridine (DMAP, 2) is known as a nucleophilic catalyst in a number of reactions, for example the Baylis–Hillman reaction [27] and the Steglich esterification [28][29]. To achieve control of the catalytic

Muyocopronones A and B: azaphilones from the endophytic fungus Muyocopron laterale

• Ken-ichi Nakashima,
• Junko Tomida,
• Tomoe Tsuboi,
• Yoshiaki Kawamura and
• Makoto Inoue

Beilstein J. Org. Chem. 2020, 16, 2100–2107, doi:10.3762/bjoc.16.177

• MTPA chloride, enolization and esterification at the C-15 position occurred preferentially over the C-3′ position. Therefore, 2.7 equivalents of the (R)- and (S)-MTPA chlorides were used to prepare the (S)- and (R)-MTPA diesters 1a and 1b, respectively (Scheme 1A). Based on the differences in chemical

Synthesis, antiinflammatory activity, and molecular docking studies of bisphosphonic esters as potential MMP-8 and MMP-9 inhibitors

• Abimelek Cortes-Pacheco,
• María Adelina Jiménez-Arellanes,
• Francisco José Palacios-Can,
• José Antonio Valcarcel-Gamiño,
• Rodrigo Said Razo-Hernández,
• María del Carmen Juárez-Vázquez,
• Adolfo López-Torres and
• Oscar Abelardo Ramírez-Marroquín

Beilstein J. Org. Chem. 2020, 16, 1277–1287, doi:10.3762/bjoc.16.108

• [23]. Then, the above-named derivatives were synthesized in a first stage by the esterification of bromoacetyl bromide and the corresponding alcohol. The reaction of ethyl or tert-butyl alcohol and bromoacetyl bromide in the presence of triethylamine in CH2Cl2 yielded the bromoaceto esters 7 and 8 in

Fluorinated phenylalanines: synthesis and pharmaceutical applications

• Laila F. Awad and
• Mohammed Salah Ayoup

Beilstein J. Org. Chem. 2020, 16, 1022–1050, doi:10.3762/bjoc.16.91

• affecting the newly introduced fluorine atom was attempted by a two-step, one-pot protocol involving an in situ esterification of a highly electrophilic pyridinium triflate intermediate [77] and afforded the anti-β-fluoro-α-amino acid methyl ester 160a in 52% yield and with 98.8% ee (Scheme 39). On the

Efficient synthesis of piperazinyl amides of 18β-glycyrrhetinic acid

• Dong Cai,
• ZhiHua Zhang,
• Yufan Meng,
• KaiLi Zhu,
• LiYi Chen,
• ChangXiang Yu,
• ChangWei Yu,
• ZiYi Fu,
• DianShen Yang and
• YiXia Gong

Beilstein J. Org. Chem. 2020, 16, 798–808, doi:10.3762/bjoc.16.73

• compound 8 involves the amidation of 18β-glycyrrhetinic acid followed by the esterification with acetic anhydride. Finally, compound 8 underwent N-Boc deprotection to prepare product 4. To ascertain the scope of the reaction, another C-3 ester derivative 17 was tested under the optimized reaction

• yield. The reaction was completed in 30 min. The principal advantages of this method are that there is no solvent required, and that the reaction time is shorter than in previous cases [16], since the acid formed during the reaction may catalyze the esterification reaction of 18β-glycyrrhetinic acid

Design and synthesis of diazine-based panobinostat analogues for HDAC8 inhibition

• Sivaraman Balasubramaniam,
• Sajith Vijayan,
• Liam V. Goldman,
• Xavier A. May,
• Kyra Dodson,
• Sweta Adhikari,
• Fatima Rivas,
• Davita L. Watkins and
• Shana V. Stoddard

Beilstein J. Org. Chem. 2020, 16, 628–637, doi:10.3762/bjoc.16.59

• esterification reaction using methanol mediated by sulfuric acid under heating conditions to provide the compound in 81% yield. The methyl ester 5 was reduced to aldehyde 6 using DIBAL-H at −78 °C. While TLC analysis revealed complete conversion of the ester to aldehyde, the isolated yield was poor (20%). The

Oligomeric ricinoleic acid preparation promoted by an efficient and recoverable Brønsted acidic ionic liquid

• Fei You,
• Xing He,
• Song Gao,
• Hong-Ru Li and
• Liang-Nian He

Beilstein J. Org. Chem. 2020, 16, 351–361, doi:10.3762/bjoc.16.34

• ]. The presence of both hydroxy and carboxy groups in the molecule of ricinoleic acid enables it to undergo intermolecular esterification, thus resulting in the formation of the oligomeric ricinoleic acid. The oligomeric ricinoleic acid with different acid value (which is an indirect index for

• excellent catalytic activity for this intermolecular esterification reaction and Brønsted acidic ionic liquids have been successfully used as catalyst in organic syntheses [29][30][31], we designed a series of Brønsted acidic ionic liquids and applied them as catalysts for the preparation of oligomeric

• depicted in Scheme 1. Results and Discussion Considering protic acids have catalytic effects on the esterification reaction, we designed and synthesized a series of ILs containing protic anions as shown in Scheme 2. With the synthesized ILs as catalyst, the ricinoleic acid esterification was performed and

A green, economical synthesis of β-ketonitriles and trifunctionalized building blocks from esters and lactones

• Daniel P. Pienaar,
• Kamogelo R. Butsi,
• Amanda L. Rousseau and
• Dean Brady

Beilstein J. Org. Chem. 2019, 15, 2930–2935, doi:10.3762/bjoc.15.287

• , atom-economical ring opening of enolizable δ-valerolactone (3, Scheme 1). Although a two-step (or four-step, should hydroxy group O-protection prove to be necessary prior to acylation) protocol could, in theory, be envisaged to produce β-ketonitrile 2 from 3 by ring-opening esterification to afford

A review of asymmetric synthetic organic electrochemistry and electrocatalysis: concepts, applications, recent developments and future directions

• Munmun Ghosh,
• Valmik S. Shinde and
• Magnus Rueping

Beilstein J. Org. Chem. 2019, 15, 2710–2746, doi:10.3762/bjoc.15.264

• ). Constant current electrolysis of 89 in a single compartment cell using a sacrificial Mg anode was conducted in the presence of a Ni catalyst and chiral ligand 90. After esterification and purification, 91 was isolated in a good yield and with moderate enantioselectivity [70]. In another recent report, Guo

Safe and highly efficient adaptation of potentially explosive azide chemistry involved in the synthesis of Tamiflu using continuous-flow technology

• Cloudius R. Sagandira and
• Paul Watts

Beilstein J. Org. Chem. 2019, 15, 2577–2589, doi:10.3762/bjoc.15.251

• continuous-flow technology. The two steps involving azide chemistry in flow are reported herein (Scheme 2), with the vision of further integrating the other steps towards continuous-flow total synthesis of this drug. To this effect, we have already reported continuous flow shikimic acid (3) esterification

Formation of alkyne-bridged ferrocenophanes using ring-closing alkyne metathesis on 1,1’-diacetylenic ferrocenes

• Celine Bittner,
• Dirk Bockfeld and
• Matthias Tamm

Beilstein J. Org. Chem. 2019, 15, 2534–2543, doi:10.3762/bjoc.15.246

• synthesized via an esterification reaction starting from symmetrical 1,1’-ferrocenoyl dichloride (3) [92] as shown in Scheme 1. To a solution of the corresponding 1-alkynol (13.5 mmol), NEt3 (13.5 mmol), and 4-dimethylaminopyridine (DMAP, 0.5 mmol) in dichloromethane (DCM, 20 mL) at 0 °C the dichloride 3 (2 g

• positions of the THF molecules are shown. Selected bond lengths [Å] and angles [°] are given in Supporting Information File 1, Tables S1 and S2. Synthesis of substrates 1 (a n = 2; b n = 3) via esterification of 3 and following RCAM with catalyst MoF6 to ferrocenophanes 2 (a: n = 2; b: n = 3); a) HO(CH2)nC

Mono- and bithiophene-substituted diarylethene photoswitches with emissive open or closed forms

• A. Lennart Schleper,
• Mariano L. Bossi,
• Vladimir N. Belov and
• Stefan W. Hell

Beilstein J. Org. Chem. 2019, 15, 2344–2354, doi:10.3762/bjoc.15.227

• ligands. The reaction with pinacolborane (HB(pin)) gave ester 9 in 97% yield [11]. Another ester (10) was synthesized by bromination of 3-thiopheneacetic acid with NBS (applying an ultrasound bath) followed by esterification of the crude product with methanol in the presence of sulfuric acid [12]. Other

Genome mining in Trichoderma viride J1-030: discovery and identification of novel sesquiterpene synthase and its products

• Xiang Sun,
• You-Sheng Cai,
• Yujie Yuan,
• Guangkai Bian,
• Ziling Ye,
• Zixin Deng and
• Tiangang Liu

Beilstein J. Org. Chem. 2019, 15, 2052–2058, doi:10.3762/bjoc.15.202

• represent the esterification reaction during the extraction process. The 5/6 bicyclic sesquiterpene identified and characterised in this study was a brasilane-type sesquiterpenoid; this sesquiterpenoid type is typically isolated from cultures of the basidiomycete Coltricia sideroides in combination with its

• characterised as a 5/6 bicyclic sesquiterpene compound 1 oxygenated at C-11. Interestingly, esterified compound 1 was isolated during the product extraction process, suggesting an esterification reaction. It contained a quaternary carbon with two methyl groups, which is uncommon of the cyclization mechanism of

A metal-free approach for the synthesis of amides/esters with pyridinium salts of phenacyl bromides via oxidative C–C bond cleavage

• Kesari Lakshmi Manasa,
• Yellaiah Tangella,
• Namballa Hari Krishna and
• Mallika Alvala

Beilstein J. Org. Chem. 2019, 15, 1864–1871, doi:10.3762/bjoc.15.182

• of a C–C bond followed by formation of a new C–N/C–O bond in the presence of K2CO3. Various pyridinium salts of phenacyl bromides can be readily transformed into a variety of amides and esters which is an alternative method for the conventional amidation and esterification in organic synthesis. High

• functional group tolerance, broad substrate scope and operational simplicity are the prominent advantages of the current protocol. Keywords: amidation; benzoylation; benzylamines; pyridinium salt of phenacyl bromides; Introduction Amidation and esterification are fundamental transformations in synthetic

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

• Gagandeep Kour Reen,
• Ashok Kumar and
• Pratibha Sharma

Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165

• ][60]. They have been employed for a number of organic reactions viz., hydrosilylation of aldehydes and ketones, acetylation reactions, redox reactions, oxidative esterification, etc. [61][62][63]. Thus, in concern with increasing demand for sustainable development, a growing number of catalytic

Electrophilic oligodeoxynucleotide synthesis using dM-Dmoc for amino protection

• Shahien Shahsavari,
• Dhananjani N. A. M. Eriyagama,
• Bhaskar Halami,
• Vagarshak Begoyan,
• Marina Tanasova,
• Jinsen Chen and
• Shiyue Fang

Beilstein J. Org. Chem. 2019, 15, 1116–1128, doi:10.3762/bjoc.15.108

• simply prepared from the commercially available 27 by esterification in ethanol. Cyclization or oligomerization of 27 was not an issue for the transformation. The primary alcohol of 28 was selectively tritylated with DMTrCl to give 29, which was phosphitylated with 13 in the presence of 14 to give 26a

Easy, efficient and versatile one-pot synthesis of Janus-type-substituted fullerenols

• Marius Kunkel and
• Sebastian Polarz

Beilstein J. Org. Chem. 2019, 15, 901–905, doi:10.3762/bjoc.15.87

• modified, are well known in the literature. These reactions can be achieved by esterification or etherification [20][21][22]. However, partial modifications are rare, especially when it comes to asymmetric substitutions [23][24]. Although, janus-type fullerenols at which only a part of the fullerene core

Synthesis of a novel category of pseudo-peptides using an Ugi three-component reaction of levulinic acid as bifunctional substrate, amines, and amino acid-based isocyanides

• Maryam Khalesi,
• Azim Ziyaei Halimehjani and
• Jürgen Martens

Beilstein J. Org. Chem. 2019, 15, 852–857, doi:10.3762/bjoc.15.82

• esterification of the α-amino acid using thionyl chloride in methanol as reagent and solvent. The second reaction is the formylation of the corresponding amino acid ester salt with ethyl formate in the presence of NaHCO3. Finally, the formamide group was transformed to the corresponding isocyanide 3 using POCl3

Synthesis of acylglycerol derivatives by mechanochemistry

• Karen J. Ardila-Fierro,
• Andrij Pich,
• Marc Spehr,
• José G. Hernández and
• Carsten Bolm

Beilstein J. Org. Chem. 2019, 15, 811–817, doi:10.3762/bjoc.15.78

• by epoxide ring-opening and esterification reactions with fatty acids 3 (Scheme 1). If successful, developing a multistep approach to prepare DAGs would contribute to the expansion of synthetic mechanochemical methodologies in ball mills [28][29][30][31], which are often limited to single-step

• esterification reactions by ball milling [44]. In practice, we milled a mixture of MAG 4a, stearic acid (3a), DCC and 4-dimethylaminopyridine (DMAP) at 25 Hz for 2 h in a mixer mill. Separation of the product by column chromatography gave DAG 5a in 97% yield (Scheme 4). Alternatively, 5a could be prepared

• following a one-pot two-step approach in the ball mill by beginning with the cobalt-catalyzed epoxide-ring opening of 2 with 3a, followed immediately by the esterification of the corresponding MAG 4a with stearic acid (3a), DCC and DMAP. Although successful, this strategy led to DAG 5a in lower yield (50

Solid-phase synthesis of biaryl bicyclic peptides containing a 3-aryltyrosine or a 4-arylphenylalanine moiety

• Iteng Ng-Choi,
• Àngel Oliveras,
• Lidia Feliu and
• Marta Planas

Beilstein J. Org. Chem. 2019, 15, 761–768, doi:10.3762/bjoc.15.72

• 9-fluorenylmethoxycarbonyl (Fmoc)/tert-butyl (t-Bu) strategy (Scheme 2). The non-commercially available amino acids Boc-Phe(4-BPin)-OH, Fmoc-Phe(4-I)-OH and Fmoc-Glu-OpNB were prepared in solution. Boc-Phe(4-BPin)-OH was obtained from Boc-Phe(4-I)-OH [27] through esterification, Miyaura borylation

Synthesis of the polyketide section of seragamide A and related cyclodepsipeptides via Negishi cross coupling

• Jan Hendrik Lang and
• Thomas Lindel

Beilstein J. Org. Chem. 2019, 15, 577–583, doi:10.3762/bjoc.15.53

• recent synthesis of plusbacin A3, Ichikawa et al. experienced similar difficulties when attempting esterification of a bulky β-OTIPS-substituted amino acid with a secondary alcohol under a variety of conditions [49]. Conclusion We developed a short synthesis of the polyketide building block present in

Syntheses and chemical properties of β-nicotinamide riboside and its analogues and derivatives

• Mikhail V. Makarov and
• Marie E. Migaud

Beilstein J. Org. Chem. 2019, 15, 401–430, doi:10.3762/bjoc.15.36

• the N1 atom of Nam occurs under these conditions. Hydrolytic de-esterification of 9a,b was achieved by a treatment with an anhydrous ammonia methanolic solution at −5 °C. Removal of benzoyl groups required prolonged reaction times (48 h versus 6 h for acetyl groups). It should be also noted that in

• after de-esterification of the tribenzoate intermediate ( +25°) using methanol saturated with dry ammonia at 2 °C for 2 days (content of β-anomer was <3%, as determined by enzymatic analyses). This result may be explained by the fact that 2,3,5-tri-O-benzoyl-D-ribofuranosylamine – although prepared by

• synthetic sequence, the key reaction of which was a coupling of bisphosphonate 34 with isopropylidene-protected NR+ 29 under the Steglich esterification conditions in the presence of tri-n-octylamine, pyridine and DCC in DMF medium at 60 °C for 18 h (Scheme 19). Compound 36 was isolated in pure form by

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

• )-5 which after O-benzylation provided an inseparable 1:3 mixture of compounds 8a and 8b. A six-carbon chain was shortened by a diol formation–diol cleavage sequence followed by aldehyde oxidation and esterification to give 9a and 9b after chromatographic separation. They were transformed into (2S,3R

• removal of the chiral auxiliary with simultaneous formation of a N-Boc derivative 30. The hydroxymethyl to carboxylate transformation to form the protected diester (2S,3R)-31 required prior basic deacetylation followed by standard oxidation and esterification. Diastereoisomer (2S,3S)-31 was also prepared

• nitrogen was protected as N-Boc to furnish (4R,5R)-47. Under basic conditions the pyrrolidin-2-one ring was cleaved to provide a five-carbon chain of the target molecule. The final steps included esterification, desilylation and selective oxidation of the hydroxymethyl group followed by esterification