Isolation and structure determination of a new analog of polycavernosides from marine Okeania sp. cyanobacterium

• Kairi Umeda,
• Naoaki Kurisawa,
• Ghulam Jeelani,
• Tomoyoshi Nozaki,
• Kiyotake Suenaga and
• Arihiro Iwasaki

Beilstein J. Org. Chem. 2024, 20, 645–652, doi:10.3762/bjoc.20.57

• compounds 1 and 5 were identical. To reveal the absolute configuration, we recorded the ECD spectrum of 1 (Figure 4) and compared it with those of 2 and 5 reported in previous papers [5][6]. We detected a Cotton effect of negative sign at around 280 nm corresponding to the n–π* transition of a ketone group

Combretastatins D series and analogues: from isolation, synthetic challenges and biological activities

• Jorge de Lima Neto and
• Paulo Henrique Menezes

Beilstein J. Org. Chem. 2023, 19, 399–427, doi:10.3762/bjoc.19.31

• ][17] by analysis of NMR and mass spectra and confirmed by X-ray crystallography in an initial report. However, attempts to determine the absolute configuration of the epoxide present in compound 1 based on crystallographic data were unsuccessful. By matching the sign of the Cotton effect curves

An accelerated Rauhut–Currier dimerization enabled the synthesis of (±)-incarvilleatone and anticancer studies

• Tharun K. Kotammagari,
• Sweta Misra,
• Sayantan Paul,
• Sunita Kunte,
• Rajesh G. Gonnade,
• Manas K. Santra and
• Asish K. Bhattacharya

Beilstein J. Org. Chem. 2023, 19, 204–211, doi:10.3762/bjoc.19.19

• 'S, 9'R (Scheme 6). After separation of individual enantiomers, we recorded the CD spectra of both enantiomers in MeOH. (−)-Incarvilleatone [(−)-1] shows a negative optical rotation and a negative Cotton effect in the CD spectrum whereas the other enantiomer (+)-incarvilleatone [(+)-1] showed a

• positive optical rotation and a positive Cotton effect in the CD spectrum (Figure S2, see Supporting Information File 1). Synthesis of (±)-incarviditone (2) Treatment of (±)-rengyolone (3) with the same base, i.e., KHMDS (2 equiv) in THF at 0 °C to rt for 24 h, resulted in the formation of a white solid

A Streptomyces P450 enzyme dimerizes isoflavones from plants

• Run-Zhou Liu,
• Shanchong Chen and
• Lihan Zhang

Beilstein J. Org. Chem. 2022, 18, 1107–1115, doi:10.3762/bjoc.18.113

• and 2 with respect to atropisomerism was assessed by chiral HPLC analysis and the comparison of experimental and calculated ECD spectra. While 1 showed a ≈3:1 atropisomer ratio, with the M-atropisomer being the major form, 2 did not exhibit a Cotton effect in the ECD measurement, suggesting that it is

Terpenoids from Glechoma hederacea var. longituba and their biological activities

• Dong Hyun Kim,
• Song Lim Ham,
• Zahra Khan,
• Sun Yeou Kim,
• Sang Un Choi,
• Chung Sub Kim and
• Kang Ro Lee

Beilstein J. Org. Chem. 2022, 18, 555–566, doi:10.3762/bjoc.18.58

• implied based on comparison of the calculated ECD spectra of 1a (aglycone of 1) and experimental ECD spectra of 1 (Figure 2B). The experimental ECD spectrum of 1 showed a negative Cotton effect at 230 nm and a positive Cotton effect at 260 nm, which showed a similarity with those of the calculated ECD

•  3C). The experimental ECD spectrum of 2 showed a negative Cotton effect at 233 nm and positive Cotton effects at 217 and 257 nm, which showed a similarity with those of calculated ECD spectrum of 1R,4R,5S,6S,8S,10S-(ent-2a). Enzyme hydrolysis and following sugar identification were performed using

Sesquiterpenes from the soil-derived fungus Trichoderma citrinoviride PSU-SPSF346

• Wiriya Yaosanit,
• Vatcharin Rukachaisirikul,
• Souwalak Phongpaichit,
• Sita Preedanon and
• Jariya Sakayaroj

Beilstein J. Org. Chem. 2022, 18, 479–485, doi:10.3762/bjoc.18.50

• spectrum of compound 1 which showed a positive Cotton effect at 227 nm (Δε +4.3, c 0.0008, MeOH), the same sign as that of compound 3, (λmax: 227 nm, Δε +4.8, c 0.0008 M, MeOH) [8] (Figure 3). Accordingly, C-11 had an R configuration. The observed specific rotation of compound 1, +46.1 (c 0.67, MeOH), was

Circularly polarized luminescent systems fabricated by Tröger's base derivatives through two different strategies

• Cheng Qian,
• Yuan Chen,
• Qian Zhao,
• Ming Cheng,
• Chen Lin,
• Juli Jiang and
• Leyong Wang

Beilstein J. Org. Chem. 2021, 17, 52–57, doi:10.3762/bjoc.17.6

• separated into two fractions R2N-TBPP and S2N-TBPP by a chiralpak IB column using MeOH/DCM (80:20, v/v) as the eluent (Supporting Information File 1, Figure S5). The CD spectrum of the first fraction exhibited a positive Cotton effect at 352 nm, assigned to R2N-TBPP, while the second one showed a negative

• Cotton effect at the same wavelength, assigned to S2N-TBPP (Figure 1a) [23]. R2N-TBPP and S2N-TBPP were tested further by CPL spectroscopy, and the magnitude of the CPL emission was estimated by a luminescence dissymmetry factor (glum), defined as 2(IL − IR )/(IL + IR) where IL and IR are the intensity

Chemical constituents of Chaenomeles sinensis twigs and their biological activity

• Joon Min Cha,
• Dong Hyun Kim,
• Lalita Subedi,
• Zahra Khan,
• Sang Un Choi,
• Sun Yeou Kim and
• Chung Sub Kim

Beilstein J. Org. Chem. 2020, 16, 3078–3085, doi:10.3762/bjoc.16.257

• , a systemic analysis of the ECD data of 13 with its diastereomers and simple derivatives showed that a positive or negative Cotton effect around 240–245 nm is indicative of the 6R or 6S configuration, respectively. From a positive Cotton effect at 245 nm of compound 1 (Figure 2C, left), the absolute

Incorporation of a metal-mediated base pair into an ATP aptamer – using silver(I) ions to modulate aptamer function

• Marius H. Heddinga and
• Jens Müller

Beilstein J. Org. Chem. 2020, 16, 2870–2879, doi:10.3762/bjoc.16.236

• were recorded (Figure S1 in Supporting Information File 1). All aptamer derivatives show a positive Cotton effect between 260 and 290 nm as well as a negative Cotton effect between 220 and 260 nm, indicating a B-type DNA structure [39]. For the most part, significant changes or trends cannot be

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

• conformers were calculated using time-dependent DFT (TDDFT) at the B3LYP/6-311+G(d,p) level of theory. The negative Cotton effect observed at 236 nm in the measured spectrum was in good agreement with that in the calculated ECD spectrum of the (7S,10R,11R)-stereoisomer (Figure 4A). Thus, the absolute

A cyclopeptide and three oligomycin-class polyketides produced by an underexplored actinomycete of the genus Pseudosporangium

• Shun Saito,
• Kota Atsumi,
• Tao Zhou,
• Keisuke Fukaya,
• Daisuke Urabe,
• Naoya Oku,
• Md. Rokon Ul Karim,
• Hisayuki Komaki and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2020, 16, 1100–1110, doi:10.3762/bjoc.16.97

• effects at 236 nm and 217 nm, respectively, which was consistent with a Cotton effect pattern predicted for the Sa-atropisomer of 1b. Moreover, the overall spectral feature of the experimental and calculated ECDs were quite similar with each other (Figure 5). Based on these results, the absolute

Synthesis and circularly polarized luminescence properties of BINOL-derived bisbenzofuro[2,3-b:3’,2’-e]pyridines (BBZFPys)

• Ryo Takishima,
• Yuji Nishii,
• Tomoaki Hinoue,
• Yoshitane Imai and
• Masahiro Miura

Beilstein J. Org. Chem. 2020, 16, 325–336, doi:10.3762/bjoc.16.32

• , indicating that the posted positions of the terminal tert-butyl groups exerted minimal influence on the Cotton effect in the solution state. A similar trend was observed for the CPL spectra. The (S)-isomers displayed left-handed CPL characteristics throughout the wavelengths of their corresponding

Pigmentosins from Gibellula sp. as antibiofilm agents and a new glycosylated asperfuran from Cordyceps javanica

• Soleiman E. Helaly,
• Wilawan Kuephadungphan,
• Patima Phainuphong,
• Mahmoud A. A. Ibrahim,
• Kanoksri Tasanathai,
• Suchada Mongkolsamrit,
• Janet Jennifer Luangsa-ard,
• Souwalak Phongpaichit,
• Vatcharin Rukachaisirikul and
• Marc Stadler

Beilstein J. Org. Chem. 2019, 15, 2968–2981, doi:10.3762/bjoc.15.293

• due to atropisomerism (Figure 2), although the TDDFT-ECD curve of (3S,3′S,6R)-1 showed a further small positive Cotton effect around 228 nm. Nevertheless, due to the high similarity of both curves, we believe that the calculated ECD data could not distinguish between (3R,3′R,6R)-1 and (3S,3′S,6R)-1

• was in accordance with our previous reports on akanthopyrones [8]. Finally, the chiral center at C-2 was previously assigned for asperfuran to have R-configuration based on the CD spectrum, which showed a negative Cotton effect at 240 nm due to the chirality at C-2, while another asperfuran derivative

• ((S)-4,6-dimethyl-2-vinyldihydrobenzofuran) showed a positive Cotton effect at the same wavelength due to the S-configuration at C-2. Since the CD spectrum of glycoasperfuran (3) showed a negative Cotton effect at 240 nm, the absolute configuration at C-2 was assigned to be R. This was also confirmed

Influence of the cis/trans configuration on the supramolecular aggregation of aryltriazoles

• Sara Tejera,
• Giada Caniglia,
• Rosa L. Dorta,
• Andrea Favero,
• Javier González-Platas and
• Jesús T. Vázquez

Beilstein J. Org. Chem. 2019, 15, 2881–2888, doi:10.3762/bjoc.15.282

• , in black), identical to those obtained for this compound in CH3CN [15], although of lower intensity. On the other hand, the ECD spectrum of the gel instead exhibited a normal Cotton effect at 253 nm (Δε = −3.8), which, at the same time, was the wavelength of its absorption maximum (Figure 6, in blue

Isolation of fungi using the diffusion chamber device FIND technology

• Benjamin Libor,
• Henrik Harms,
• Stefan Kehraus,
• Ekaterina Egereva,
• Max Crüsemann and
• Gabriele M. König

Beilstein J. Org. Chem. 2019, 15, 2191–2203, doi:10.3762/bjoc.15.216

• ) spectra. The latter ones were performed by Wu et al. using (2S,6S)-verbenone and (2R,6R)-verbenone and can be applied here, because of the assumed minor effect of the side chain on the CD spectrum [21]. Experimental data for 1 showed a negative Cotton effect in the range of 320–350 nm (321 nm), which

• , C-6 and C-7 to be the same as in 1. The CD spectrum of 2 showed also a negative Cotton effect as 1, indicating the absolute configurations of C-2, C-6 and C-7 to be all S (see Supporting Information File 1, Figure S3 for the CD spectrum of 2). The configuration at C-11 could not be determined. Thus

Bipolenins K–N: New sesquiterpenoids from the fungal plant pathogen Bipolaris sorokiniana

• Chin-Soon Phan,
• Hang Li,
• Simon Kessler,
• Peter S. Solomon,
• Andrew M. Piggott and
• Yit-Heng Chooi

Beilstein J. Org. Chem. 2019, 15, 2020–2028, doi:10.3762/bjoc.15.198

• and other reported analogues based on NOESY correlations (Figure 3), while the configuration at C-2 was not determined. The ECD spectrum of 4 (Figure S38, Supporting Information File 1) was measured, but no significant Cotton effect was observed. Therefore, the structure of 4 was determined as shown

Synthesis, enantioseparation and photophysical properties of planar-chiral pillar[5]arene derivatives bearing fluorophore fragments

• Guojuan Li,
• Chunying Fan,
• Guo Cheng,
• Wanhua Wu and
• Cheng Yang

Beilstein J. Org. Chem. 2019, 15, 1601–1611, doi:10.3762/bjoc.15.164

• fractions observed at 270–320 nm are perfect mirror images, thus confirming that the two fractions contain a pair of enantiomers. The positive Cotton effect observed at ca. 310 nm was assigned to the Rp configured enantiomer whereas the negative Cotton effect at ca. 310 nm was assigned to the corresponding

An azobenzene container showing a definite folding – synthesis and structural investigation

• Abdulselam Adam,
• Saber Mehrparvar and
• Gebhard Haberhauer

Beilstein J. Org. Chem. 2019, 15, 1534–1544, doi:10.3762/bjoc.15.156

• is dominated by only one transition (n→π*). Accordingly, the conformation (M or P) of the cis-azobenzene moiety can directly be identified from the sign of the Cotton effect at 450 nm. Previous studies have demonstrated that the cis-(M) isomer shows a positive and the cis-(P) isomer has a negative

• Cotton effect in this region [43][49]. If this is taken into account, it becomes obvious that the cis,cis-isomer adopts the M,M conformation. This is in line with the DFT calculations finding only the cis,cis-(M,M) isomer as minimum on the energy potential surface. The spectrum of cis,trans-10 allows the

Pyrene–nucleobase conjugates: synthesis, oligonucleotide binding and confocal bioimaging studies

• Artur Jabłoński,
• Yannic Fritz,
• Hans-Achim Wagenknecht,
• Rafał Czerwieniec,
• Tytus Bernaś,
• Damian Trzybiński,
• Krzysztof Woźniak and
• Konrad Kowalski

Beilstein J. Org. Chem. 2017, 13, 2521–2534, doi:10.3762/bjoc.13.249

• chromophores [19][20][21]. This helical twist was evidenced by circular dichroism, in particular a strong bisignate Cotton effect for the DNA-templated pyrene assemblies [19][20]. Figure 1 shows selected examples of pyrene-modified nucleic acids and nucleosides. On the other hand, pyrene–nucleobase conjugates

Secondary metabolome and its defensive role in the aeolidoidean Phyllodesmium longicirrum, (Gastropoda, Heterobranchia, Nudibranchia)

• Alexander Bogdanov,
• Cora Hertzer,
• Stefan Kehraus,
• Samuel Nietzer,
• Sven Rohde,
• Peter J. Schupp,
• Heike Wägele and
• Gabriele M. König

Beilstein J. Org. Chem. 2017, 13, 502–519, doi:10.3762/bjoc.13.50

• configuration at C-2 for 8 and 9 was established with the help of CD experiments (Supporting Information File 1, Figures S22 and S27). According to Kobayashi et al. [31] (S) configuration at C-2 in furanocembranoids causes a negative Cotton effect at 246 nm like we obtained for compound 8, which is thus (2S

• )-isosarcophine. The CD spectrum of 9 was the inverse of 8 and displayed a positive Cotton effect at 246 nm demonstrating that 8 and 9 are diastereomers. Thus, compound 9 is 2R-isosarcophine. The cembranoid bisepoxide 12 was isolated as colorless oil, with a specific optical rotation of [α]D20 −44.6 (c 3.3 in

• dihydrofuran ring. Previous studies on the stereochemistry of furanocembranoids [31][36][38][39] stated a relation between the value of the specific optical rotation, the CD Cotton effect and the configuration at C-2. Thus, a large positive specific rotation value corresponds with S configuration at C-2

Biomimetic synthesis and HPLC–ECD analysis of the isomers of dracocephins A and B

• Viktor Ilkei,
• András Spaits,
• Anita Prechl,
• Áron Szigetvári,
• Zoltán Béni,
• Miklós Dékány,
• Csaba Szántay Jr,
• Judit Müller,
• Árpád Könczöl,
• Ádám Szappanos,
• Attila Mándi,
• Sándor Antus,
• Ana Martins,
• Attila Hunyadi,
• György Tibor Balogh,
• György Kalaus (†),
• Hedvig Bölcskei,
• László Hazai and
• Tibor Kurtán

Beilstein J. Org. Chem. 2016, 12, 2523–2534, doi:10.3762/bjoc.12.247

• , whose negative 327 nm n–π* Cotton effect (CE) and the positive 289 nm π–π* CE were correlated with M helicity of the fused hetero ring and (2R) absolute configuration [8][9]. The mirror image HPLC–ECD spectra of (R)- and (S)-naringenin were recorded after separating the enantiomers on a Chiralpack IA

New furoisocoumarins and isocoumarins from the mangrove endophytic fungus Aspergillus sp. 085242

• Ze’en Xiao,
• Senhua Chen,
• Runlin Cai,
• Shao’e Lin,
• Kui Hong and
• Zhigang She

Beilstein J. Org. Chem. 2016, 12, 2077–2085, doi:10.3762/bjoc.12.196

• hybridized methylene (δC 36.0, δH 3.02) and methine (δC 74.7, δH 4.70) signals. HMBC correlations from H-10 (δH 2.12) to C-6 and C-7 and COSY correlations of H-7 with H-6 and H-10 further supported the above deduction (Figure 2). Finally, negative cotton effect (λ = 265 nm, Δε = −15.10) observed in the ECD

Chiroptical properties of 1,3-diphenylallene-anchored tetrathiafulvalene and its polymer synthesis

• Masashi Hasegawa,
• Junta Endo,
• Seiya Iwata,
• Toshiaki Shimasaki and
• Yasuhiro Mazaki

Beilstein J. Org. Chem. 2015, 11, 972–979, doi:10.3762/bjoc.11.109

• orientation of the chromophores [8][9]. We recently introduced 1,3-bis(tetrathiafulvalenyl)allene derivatives 1, as a new class of chiral electrochromic (EC) materials consisting of redox-active chromophores and a non-centrochiral framework (Figure 1) [10]. The intensive Cotton effect on the ECD spectra is

• using TD-DFT calculations [21]. Thus, the intensive Cotton effect is associated with the exciton coupling of the two chromophores of the iodobenzene units. In the ECD spectrum of (+)-9, the mirror image of the trend lines of (−)-9 was found. The UV–vis absorption spectrum of 3 exhibits absorption maxima

• at 314 and 405 nm. In the ECD spectra of (+)/(−)-3, the Cotton effect was observed over the entire absorption range. A simulated spectrum of 3 with the (R)-configuration, calculated by TD-DFT (B3LYP/6-31G(d,p)), has moderate resemblance to the spectrum obtained from (−)-3. This result is also

Trogopterins A–C: Three new neolignans from feces of Trogopterus xanthipes

• Soyoon Baek,
• Xuikui Xia,
• Byung Sun Min,
• Chanil Park and
• Sang Hee Shim

Beilstein J. Org. Chem. 2014, 10, 2955–2962, doi:10.3762/bjoc.10.313

• comparing the circular dichroism (CD) data to those of previously reported neoligans containing a dihydrobenzofuran skeleton [17]. The CD of compound 1 showed positive cotton effects at 255 and 327 nm along with a negative cotton effect at 234 nm. These features were very similar to those of neolignans [17

Preparation of neuroprotective condensed 1,4-benzoxazepines by regio- and diastereoselective domino Knoevenagel–[1,5]-hydride shift cyclization reaction

• László Tóth,
• Yan Fu,
• Hai Yan Zhang,
• Attila Mándi,
• Katalin E. Kövér,
• Tünde-Zita Illyés,
• Attila Kiss-Szikszai,
• Balázs Balogh,
• Tibor Kurtán,
• Sándor Antus and
• Péter Mátyus

Beilstein J. Org. Chem. 2014, 10, 2594–2602, doi:10.3762/bjoc.10.272

• broad positive Cotton effect (CE) at 378 nm, negative ones at 314, 305, 272 nm and positive ones at 284, 279 and 224 nm (Figure 4a). The HPLC-ECD spectrum of the first-eluting enantiomer of 7b showed similar ECD pattern with somewhat different shape and intensities in the 290–240 nm range (Figure 4b