Synthesis and HDAC inhibitory activity of pyrimidine-based hydroxamic acids

• Virginija Jakubkiene,
• Gabrielius Ernis Valiulis,
• Markus Schweipert,
• Asta Zubriene,
• Daumantas Matulis,
• Franz-Josef Meyer-Almes and
• Sigitas Tumkevicius

Beilstein J. Org. Chem. 2022, 18, 837–844, doi:10.3762/bjoc.18.84

• Melting points were determined in open capillaries with a digital melting point IA9100series apparatus (ThermoFisher Scientific). All reactions and purity of the synthesized compounds were monitored by TLC using silica gel 60 F254 aluminum plates (Merck). Visualization was accomplished by UV light. Column

• chromatography was performed using silica gel 60 (0.040–0.063 mm) (Merck). NMR spectra were recorded on a Bruker Ascend 400 spectrometer (400 MHz and 100 MHz for 1H and 13C, respectively). 1H NMR and 13C NMR were referenced to residual solvent peaks. High-resolution mass spectrometry (HRMS) analyses were carried

Thiophene/selenophene-based S-shaped double helicenes: regioselective synthesis and structures

• Mengjie Wang,
• Lanping Dang,
• Wan Xu,
• Zhiying Ma,
• Liuliu Shao,
• Guangxia Wang,
• Chunli Li and
• Hua Wang

Beilstein J. Org. Chem. 2022, 18, 809–817, doi:10.3762/bjoc.18.81

• ]. Column chromatography was carried out on silica gel (300–400 mesh). Analytical thin-layer chromatography was performed on glass plates of silica gel GF-254 with detection by UV. Standard techniques for synthesis under inert atmosphere and Schlenk glassware equipped with an 8 mm PTFE vacuum stopcock, were

Identification of the new prenyltransferase Ubi-297 from marine bacteria and elucidation of its substrate specificity

• Jamshid Amiri Moghaddam,
• Huijuan Guo,
• Karsten Willing,
• Thomas Wichard and
• Christine Beemelmanns

Beilstein J. Org. Chem. 2022, 18, 722–731, doi:10.3762/bjoc.18.72

• methanol (1.0 L), dried under vacuum, and the resultant MeOH extract was then extracted with hexane (120 mL) and dried again under vacuum. The hexane extract was purified by flash chromatography (Biotage Isolera Prime) over a silica gel column (eluent: cyclohexane/EtOAc 100:0 to 80:20 to 0:100). The

Direct C–H amination reactions of arenes with N-hydroxyphthalimides catalyzed by cuprous bromide

• Dongming Zhang,
• Bin Lv,
• Pan Gao,
• Xiaodong Jia and
• Yu Yuan

Beilstein J. Org. Chem. 2022, 18, 647–652, doi:10.3762/bjoc.18.65

• -layer chromatography (TLC) on gel F254 plates. Flash column chromatograph was carried out using 300–400 mesh silica gel at medium pressure. General procedure for synthesis of 3a–u: N-Hydroxyphthalimide (0.1 mmol), CuBr (40 mol %, 0.04 mmol), triethyl phosphite (6.0 equiv, 0.6 mmol) and (hetero)arene (2

• mL) were added into a 15 mL sealed tube. The resulting mixture was stirred at 100 °C under air for 12 h, and the progress was monitored by TLC. The solution was then cooled to room temperature and the solvent was removed under vacuum. The crude residue was purified by column chromatography on silica

• gel (ethyl acetate/petroleum ether 1:10) to afford the desired products 3a–u. Amination of arenes with phthalimides. Substrate scope of the copper-catalyzed C–H imidation of arenes. Reaction conditions: 1 (2.0 mL as substrate and solvent), 2a (0.10 mmol), CuBr (0.04 mmol) and P(OEt)3 (0.6 mmol) were

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

• was performed using a Gilson 321 pump with a Shodex Refractive Index Detector, an INNO column C18 5 μm column (250 × 10 mm), and a Lux 5 μm Cellulose-1 column (250 × 4.6 mm). Silica gel 60 (Merck, 70–230 mesh and 230–400 mesh), RP-C18 silica gel (Merck, 230–400 mesh), Sephadex LH-20 (Parmacia Co

• ., Japan), and Diaion HP-20 (Mitsubishi Chemical Co., Japan) were used for column chromatography. Merck precoated silica gel F254 plates and reversed-phase (RP)-18 F254s plates (Merck) were used for thin-layer chromatography (TLC). Spots of compounds on TLC were detected under UV light or by heating after

• to a silica gel column (CHCl3/MeOH, 20:1 → 1:1) to give five fractions (C1–C5). Fraction C2 (3.0 g) was applied to an RP-C18 silica gel column (50% MeOH) to give 12 subfractions (C2a–C2l). Compound 6 (4 mg, tR = 25.9 min) was yielded by purifying subfraction C2h (32 mg) using a semipreparative HPLC

Substituent effect on TADF properties of 2-modified 4,6-bis(3,6-di-tert-butyl-9-carbazolyl)-5-methylpyrimidines

• Irina Fiodorova,
• Tomas Serevičius,
• Rokas Skaisgiris,
• Saulius Juršėnas and
• Sigitas Tumkevicius

Beilstein J. Org. Chem. 2022, 18, 497–507, doi:10.3762/bjoc.18.52

• were not corrected. Thin-layer chromatography was performed using TLC aluminum sheets with silica gel (Merck 60 F254). Visualization was accomplished by UV light. Column chromatography was performed using silica gel 60 (0.040–0.063 mm, Merck). NMR spectra were recorded on a Bruker Ascend 400 (400 MHz

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

• -2000 polarimeter. ESI-TOF mass spectra were obtained using a TOF/Q-TOF Mass spectrometer. Thin-layer chromatography (TLC) and preparative TLC were performed on silica gel 60 GF254 (Merck). Column chromatography (CC) was conducted on silica gel (Merck) type 100 (70–230 mesh ASTM) and type 60 (230–400

• mesh ASTM), Sephadex LH-20, or reversed-phase C18 silica gel. Fungal material The fungus PSU-SPSF346 was isolated from a soil sample collected from the Sirindhorn Peat Swamp Forest, Narathiwat Province, Thailand. This fungus was deposited as BCC88125 at BIOTEC Culture Collection (BCC), National Center

• ). Subfraction A4F6 (770.3 mg) was separated by CC over silica gel using a mixture of EtOAc/CH2Cl2/MeOH 18:1:1 to give 12 subfractions (A4F6A–A4F6L). Subfraction A4F6H contained compound 3 (91.3 mg). Subfraction A4F6J (532.4 mg) afforded compound 4 (178.3 mg) after purification by CC over reversed-phase C18

Tosylhydrazine-promoted self-conjugate reduction–Michael/aldol reaction of 3-phenacylideneoxindoles towards dispirocyclopentanebisoxindole derivatives

• Sayan Pramanik and
• Chhanda Mukhopadhyay

Beilstein J. Org. Chem. 2022, 18, 469–478, doi:10.3762/bjoc.18.49

• reaction was checked by TLC glass sheets pre-coated with silica gel (with binder, 300 mesh, Spectrochem) and column chromatography was performed using silica gel (100–200 mesh). Bruker 300 MHz and 400 MHz instruments were used for 1H and 13C NMR spectra at 300 MHz, 400 MHz and 75 MHz, 100 MHz respectively

• EtOAc (3 × 10 mL). The organic layers were combined and washed with brine, then dried over anhydrous Na2SO4. After the solvent was removed under reduced pressure, the crude product was purified by column chromatography using 100–200 mesh silica gel and petroleum ether–ethyl acetate mixture as the eluent

Cs₂CO₃-Promoted reaction of tertiary bromopropargylic alcohols and phenols in DMF: a novel approach to α-phenoxyketones

• Ol'ga G. Volostnykh,
• Olesya A. Shemyakina,
• Anton V. Stepanov and
• Igor' A. Ushakov

Beilstein J. Org. Chem. 2022, 18, 420–428, doi:10.3762/bjoc.18.44

• chromatography was performed on silica gel 60 (230–400 mesh, particle size 0.040–0.063 mm, Merck). Bromopropargylic alcohols 1a–c and chloropropargylic alcohol were prepared according to published methods [22][23][59]. Phenol (2a), naphthalen-1-ol (2b), naphthalen-2-ol (2c), 4-nitrophenol (2d), 2-nitrophenol (2e

• mixture was stirred at 50–55 °C for 3 h, filtered and concentrated. The residue was purified by flash column chromatography on silica gel (5.0 × 4.0 cm, gradient elution, C6H14/Et2O, 2:1 followed by Et2O, Me2CO) to give products 3a (10 mg, 4%), 4a (214 mg, 55%), 5a (30 mg, 22%) and 7 (11 mg, 5%). Scope of

Four bioactive new steroids from the soft coral Lobophytum pauciflorum collected in South China Sea

• Di Zhang,
• Zhe Wang,
• Xiao Han,
• Xiao-Lei Li,
• Zhong-Yu Lu,
• Bei-Bei Dou,
• Wen-Ze Zhang,
• Xu-Li Tang,
• Ping-Lin Li and
• Guo-Qiang Li

Beilstein J. Org. Chem. 2022, 18, 374–380, doi:10.3762/bjoc.18.42

• J-815 CD spectropolarimeter. Optical rotations were measured with a Jasco P-1020 polarimeter. Semi-preparative HPLC (Agilent Technologies 1260 Infinity II) equipped with a reversed-phase column ((YMC-packed C18, 5 µm, 250 × 10 mm, 2.0 mL/min) was used to purify samples. Silica gel (300–400 mesh

• , Qingdao) was used for column chromatography (CC), and precoated silica gel plates (GF254, Qingdao) were used for TLC. Soft coral material The soft coral Lobophytum pauciflorum was collected from Yongle Islands of Xisha Islands of the South China Sea in May 2012. The sample was identified by Pingjyun Sung

• subjected to silica gel column chromatography (CC) eluted with two gradient systems, PE/acetone (1:0 to 1:1) and subsequently CH2Cl2/MeOH (15:1 to 1:1) to afford 8 fractions. Fraction 4 (14.6 g) was split (chromatographed on) by silica gel eluting with a gradient of PE/acetone (30:1 to 1:1) to give three

Amamistatins isolated from Nocardia altamirensis

• Till Steinmetz,
• Wolf Hiller and
• Markus Nett

Beilstein J. Org. Chem. 2022, 18, 360–367, doi:10.3762/bjoc.18.40

• supernatant by filtration, the adsorbed compounds were eluted from the resin with methanol. The resulting extract was concentrated to dryness and a first preliminary fractionation was accomplished by flash column chromatography on reversed-phase silica gel using increasing concentrations of methanol in water

Organocatalytic asymmetric nitroso aldol reaction of α-substituted malonamates

• Ekta Gupta,
• Narendra Kumar Vaishanv,
• Sandeep Kumar,
• Raja Krishnan Purshottam,
• Ruchir Kant and
• Kishor Mohanan

Beilstein J. Org. Chem. 2022, 18, 217–224, doi:10.3762/bjoc.18.25

• (100–200 mesh silica gel) using EtOAc/hexane as the eluent to afford product 4a as white solid (71 mg, 90%). Rf 0.20 (EtOAc/hexane 3:7); mp 115–117 °C; 1H NMR (400 MHz, CDCl3) δ 9.04 (s, 1H), 7.47–7.44 (m, 5H), 7.31–7.26 (m, 2H), 7.20–7.14 (m, 3H), 3.81 (s, 3H), 1.59 (s, 3H) ppm; 13C NMR (100 MHz

• silica gel column chromatography. Enantioselectivities were determined by chiral HPLC analysis. Variation of ester moiety of malonamates and nitrosoarenes. General conditions: 1 (0.20 mmol), 2a (0.24 mmol), 3a (0.04 mmol), toluene (3.0 mL). Yields refer to isolated yields after silica gel column

Anomeric 1,2,3-triazole-linked sialic acid derivatives show selective inhibition towards a bacterial neuraminidase over a trypanosome trans-sialidase

• Peterson de Andrade,
• Sanaz Ahmadipour and
• Robert A. Field

Beilstein J. Org. Chem. 2022, 18, 208–216, doi:10.3762/bjoc.18.24

• (P3657) and DANA (D9050) were purchase from Sigma-Aldrich. Neuraminidase from Clostridium perfringens (C. Welchii) was purchased from Sigma-Aldrich (N2876-6U) and Milli-Q water was used to prepare all buffers. Thin-layer chromatography (TLC) was performed on pre-coated silica gel 60 F254 plates (Merck

Glycosylated coumarins, flavonoids, lignans and phenylpropanoids from Wikstroemia nutans and their biological activities

• Meifang Wu,
• Xiangdong Su,
• Yichuang Wu,
• Yuanjing Luo,
• Ying Guo and
• Yongbo Xue

Beilstein J. Org. Chem. 2022, 18, 200–207, doi:10.3762/bjoc.18.23

• performed using silica gel (200–300 mesh and H, Qingdao Marine Chemical Co. Ltd., Qingdao, People's Republic of China), RP-18 gel (40–63 μm, Merck, Darmstadt, Germany), and MCI gel (75–150 μm; Mitsubishi Chemical Corporation, Japan). Fractions were monitored by TLC (GF254, Qingdao Marine Chemical Co. Ltd

• ., Qingdao), and spots were visualized by heating silica gel plates sprayed with 10% H2SO4 in EtOH. All solvents were distilled prior to use. Plant materials The dried stems and roots of W. nutans were collected in Xinzhou City of Guangxi Province, People’s Republic of China, in August 2019, and

• and EtOAc. The EtOAc extract (EE) fraction (110 g) was chromatographed over a silica gel (100–200 mesh) column (20 × 100 cm), eluted with dichloromethane/methanol (50:1 to 0:1 v/v) to afford 10 fractions (EE1-EE10). The fraction EE4 (13.3 g) was further purified by semi-preparative HPLC [phenyl column

Multi-faceted reactivity of N-fluorobenzenesulfonimide (NFSI) under mechanochemical conditions: fluorination, fluorodemethylation, sulfonylation, and amidation reactions

• José G. Hernández,
• Karen J. Ardila-Fierro,
• Dajana Barišić and
• Hervé Geneste

Beilstein J. Org. Chem. 2022, 18, 182–189, doi:10.3762/bjoc.18.20

• ). To mitigate this, the milling experiment was repeated using silica gel (SiO2) as a milling auxiliary. The use of SiO2 did not affect significantly the product composition of the reaction as determined by NMR analysis of an independent experiment milling 1c and NFSI (2.0 equiv) at 30 Hz for 3 h. This

Green synthesis of C5–C6-unsubstituted 1,4-DHP scaffolds using an efficient Ni–chitosan nanocatalyst under ultrasonic conditions

• Soumyadip Basu,
• Sauvik Chatterjee,
• Suman Ray,
• Suvendu Maity,
• Prasanta Ghosh,
• Asim Bhaumik and
• Chhanda Mukhopadhyay

Beilstein J. Org. Chem. 2022, 18, 133–142, doi:10.3762/bjoc.18.14

• TAKASHI ultrasonic cleaning bath, and the progress of the reactions was monitored by TLC analysis using silica gel. 1H and 13C NMR spectra were recorded on Bruker 300 MHz and 400 MHz instruments using CDCl3, with TMS as internal reference. Melting points were recorded on an electrical melting point

• and purification of the residue via silica gel (100–200 mesh) column chromatography using ethyl acetate/petroleum ether (bp 60–80 °C) as eluent. FTIR spectra of (a) the Ni–chitosan NPs and (b) bare chitosan. PXRD data for the Ni–chitosan NPs. TEM (a and b) and SEM images (c and d) of the Ni–chitosan

Tenacibactins K–M, cytotoxic siderophores from a coral-associated gliding bacterium of the genus Tenacibaculum

• Yasuhiro Igarashi,
• Yiwei Ge,
• Tao Zhou,
• Amit Raj Sharma,
• Enjuro Harunari,
• Naoya Oku and
• Agus Trianto

Beilstein J. Org. Chem. 2022, 18, 110–119, doi:10.3762/bjoc.18.12

• separated from the aqueous layer containing the mycelium. Evaporation of the solvent gave 6.54 g of extract from 3 L of culture. The extract (6.54 g) was subjected to silica gel column chromatography with a step gradient of CHCl3/MeOH 1:0, 20:1, 10:1, 4:1, 2:1, 1:1, and 0:1 (v/v). Fraction 4 (4:1) was

Efficient and regioselective synthesis of dihydroxy-substituted 2-aminocyclooctane-1-carboxylic acid and its bicyclic derivatives

• İlknur Polat,
• Selçuk Eşsiz,
• Uğur Bozkaya and
• Emine Salamci

Beilstein J. Org. Chem. 2022, 18, 77–85, doi:10.3762/bjoc.18.7

• a mixture of products 10 and 11 in a 7:3 ratio was determined by NMR spectroscopy. The reaction mixture was purified using preparative silica gel TLC on a chromatotron with ethyl acetate/hexane (50:50) as the eluent to give carbamate 10 and diol isomer mixture 11 in 65% and 25% yields, respectively

• (Figure 2) [28]. The formation of lactone 10 can again be explained by participation of the neighbouring group, as discussed above. However, during the purification on silica gel of the lactone-Boc product, its transesterification also resulted in corresponding methyl carbamate 10. We then investigated

Efficient synthesis of ethyl 2-(oxazolin-2-yl)alkanoates via ethoxycarbonylketene-induced electrophilic ring expansion of aziridines

• Yelong Lei and
• Jiaxi Xu

Beilstein J. Org. Chem. 2022, 18, 70–76, doi:10.3762/bjoc.18.6

• , MeCN, and 1,4-dioxane were refluxed over CaH2; toluene was refluxed over Na with benzophenone as an indicator, and all solvents were freshly distilled prior to use. Flash column chromatography was performed using silica gel (normal phase, 200–300 mesh) from Branch of Qingdao Haiyang Chemical. Petroleum

• ether (PE) used for column chromatography was the 60–90 °C fraction, and the removal of residual solvent was accomplished under rotovap. Reactions were monitored by thin-layer chromatography on silica gel GF254 coated 0.2 mm plates from Institute of Yantai Chemical Industry. Microwave-assisted reactions

• (0.36 mmol) and aziridine 2 (0.30 mmol) were added to DCE (1.0 mL) in a sealed 10 mL microwave tube. The resulting solution was stirred at 130 °C for 20 min under microwave heating. After the reaction was completed, the resulting mixture was evaporated in vacuo. The crude residue was purified by silica

Bifunctional thiourea-catalyzed asymmetric [3 + 2] annulation reactions of 2-isothiocyanato-1-indanones with barbiturate-based olefins

• Jiang-Song Zhai and
• Da-Ming Du

Beilstein J. Org. Chem. 2022, 18, 25–36, doi:10.3762/bjoc.18.3

• silica gel (200–300 mesh). Melting points were determined with an XT-4 melting-point apparatus and are uncorrected. 1H NMR spectra were measured with a Bruker Ascend 400 MHz spectrometer, chemical shifts are reported in δ (ppm) units relative to tetramethylsilane (TMS) as an internal standard. 13C NMR

• 1 (0.06 mmol), 2 (0.05 mmol), Et3N (1.0 mg, 0.01 mmol, 0.2 equiv), and DCM (1.0 mL). The mixture was stirred at room temperature for 12 h, then the reaction mixture was concentrated and directly purified by silica gel column chromatography to afford the racemates of 3. 2. Procedure for the synthesis

• of chiral compounds 3 To a dried small bottle were added 1 (0.12 mmol), 2 (0.10 mmol), chiral organocatalyst C4 (2.7 mg, 0.005 mmol, 5 mol %), and DCM (1.0 mL). The mixture was stirred at room temperature for 12‒40 h, then the reaction mixture was concentrated and directly purified by silica gel

Unsaturated fatty acids and a prenylated tryptophan derivative from a rare actinomycete of the genus Couchioplanes

• Shun Saito,
• Kanji Indo,
• Naoya Oku,
• Hisayuki Komaki,
• Masashi Kawasaki and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2021, 17, 2939–2949, doi:10.3762/bjoc.17.203

• extracted with 1-butanol. The extract (4.4 g from 3 L) was sequentially fractionated by column chromatographies on silica gel and ODS, and the resulting fractions were purified by reverse-phase HPLC to give 1 (5.2 mg), 2 (2.3 mg), 3 (1.0 mg), 4 (6.3 mg), and 5 (8.0 mg). The molecular formula of 1 was

• between the diastereomer pairs. The enantiomer ratio of 4 was estimated to be S/R = 56:44 or near by chiral phase HPLC analysis of 4' on a cellulose tribenzoate-coated silica gel column (Figure 4). Thus, 4 was concluded to be an enantiomeric mixture of (2E,4E)-7-hydroxy-2,4-dimethyl-2,4-octadienoic acid

• recorded on a Bruker micrOTOF spectrometer. Silica gel 60 (spherical) (Kanto Chemical Co., Inc.) was used for silica gel column chromatography. Cosmosil 75C18-PREP (Nacalai Tesque, Inc.) was used for ODS column chromatography. Routine HPLC separations were performed on an Agilent HP1200 system, and chiral

First total synthesis of hoshinoamide A

• Haipin Zhou,
• Zihan Rui,
• Yiming Yang,
• Shengtao Xu,
• Yutian Shao and
• Long Liu

Beilstein J. Org. Chem. 2021, 17, 2924–2931, doi:10.3762/bjoc.17.201

• 2-chlorotrityl chloride (CTC) resin with 8 (4 equiv) and DIPEA successfully produced the resin-bound tripeptide 3 in good yield [17]. It should be noted that unreacted 8 can be largely recovered by a quick silica gel chromatography. The N terminus of 3 was then sequentially extended with properly

A two-phase bromination process using tetraalkylammonium hydroxide for the practical synthesis of α-bromolactones from lactones

• Yuki Yamamoto,
• Akihiro Tabuchi,
• Kazumi Hosono,
• Takanori Ochi,
• Kento Yamazaki,
• Shintaro Kodama,
• Akihiro Nomoto and
• Akiya Ogawa

Beilstein J. Org. Chem. 2021, 17, 2906–2914, doi:10.3762/bjoc.17.198

• layer was washed with H2O (10 mL × 2), dried by anhydrous Na2SO4, then filtered. The filtrate was concentrated under reduced pressure. Finally, the residue was purified by silica-gel column chromatography (AcOMe/isohexane) to give pure product 5. One-pot synthesis of a functional lactone 6 using PhS−Na

• concentrated under reduced pressure. Finally, the residue was purified by silica-gel column chromatography (Et2O/isohexane) to give pure product 6. General procedure for α-bromination of δ-valerolactone (1a) and the method described in this work. Tetraalkylammonium salt-mediated intramolecular cyclization of

Selective sulfonylation and isonitrilation of para-quinone methides employing TosMIC as a source of sulfonyl group or isonitrile group

• Chuanhua Qu,
• Run Huang,
• Yong Li,
• Tong Liu,
• Yuan Chen and
• Guiting Song

Beilstein J. Org. Chem. 2021, 17, 2822–2831, doi:10.3762/bjoc.17.193

• the reaction mixture was heated under microwave irradiation at 90 °C for 10 min and monitored by TLC until starting material was consumed. Then, the reaction mixture was concentrated under reduced pressure followed by column chromatography over silica gel using petroleum/EtOAc (0 to 10%) as eluent to

• mixture was stirred at 80 °C for 10 h and monitored by TLC. Then, the reaction mixture was concentrated under reduced pressure followed by column chromatography over silica gel using petroleum/EtOAc 10:1 to ≈5:1 as eluent to afford the desired product 4. Selected bioactive compounds. Crystal structure of

Biological properties and conformational studies of amphiphilic Pd(II) and Ni(II) complexes bearing functionalized aroylaminocarbo-N-thioylpyrrolinate units

• Samet Poyraz,
• Samet Belveren,
• Sabriye Aydınoğlu,
• Mahmut Ulger,
• Abel de Cózar,
• Maria de Gracia Retamosa,
• Jose M. Sansano and
• H. Ali Döndaş

Beilstein J. Org. Chem. 2021, 17, 2812–2821, doi:10.3762/bjoc.17.192

• silica gel 60 (230–400 mesh). Kieselgel columns were packed with silica gel GF254 (Merck 7730). Flash chromatography was carried out on handpacked columns of Merck silica gel 60 (0.040–0.063 mm). Melting points were determined on a Stuart SMP3 hot stage apparatus. The structurally most important peaks of