Isolation and biosynthesis of daturamycins from Streptomyces sp. KIB-H1544

• Yin Chen,
• Jinqiu Ren,
• Ruimin Yang,
• Jie Li,
• Sheng-Xiong Huang and
• Yijun Yan

Beilstein J. Org. Chem. 2022, 18, 1009–1016, doi:10.3762/bjoc.18.101

• , 20 mM imidazole, pH 8.0). After ultrasonic cell crushing, the cells were centrifuged at 24,000 rpm for 60 min to remove cell fragments. The supernatant was filtered through 0.22 μm of the filter membrane and then loaded into the nickel column of the rebalanced lysate (HisTraqTM FF, GE Healthcare

• ). The eluent was removed with buffer B (50 mM Tris-HCl, 300 mM NaCl, 250 mM imidazole, pH 8.0) at a flow rate of 2 mL/min, starting from the fourth tube of the collection tube and ending at the sixth tube. The outgoing protein was collected and poured into a precooled filter column (Ultracel series 10

• KDa; GE Healthcare). Then, the collected DatA (or EchA) protein was concentrated and buffer-exchanged into storage buffer (50 mM NaH2PO4, 100 mM NaCl, pH 8.0, containing 10% glycerin). The proteins were tested by SDS-PAGE, frozen using liquid nitrogen, and kept at −80 °C. In vitro reactions DatA

On Reuben G. Jones synthesis of 2-hydroxypyrazines

• Pierre Legrand and
• Yves L. Janin

Beilstein J. Org. Chem. 2022, 18, 935–943, doi:10.3762/bjoc.18.93

• was made acidic with 37% hydrochloric acid (3.3 mL, 39.31 mmol), diluted in water (150 mL), and stirred for 15 minutes. A saturated solution of sodium hydrogencarbonate was then slowly added to bring the pH to 6, this was extracted with ethyl acetate (3 × 50 mL) and the organic layer was washed with

• sodium hydrogencarbonate was then slowly added to bring the pH to 6, this was extracted with ethyl acetate (3 × 50 mL) and the organic layer was washed with brine (30 mL), dried over magnesium sulfate, and concentrated to dryness. The residue was purified by a chromatography over silica gel (cyclohexane

Synthetic strategies for the preparation of γ-phostams: 1,2-azaphospholidine 2-oxides and 1,2-azaphospholine 2-oxides

• Jiaxi Xu

Beilstein J. Org. Chem. 2022, 18, 889–915, doi:10.3762/bjoc.18.90

• -azaphosphole 2-oxide (95a) in the lowest yield. The (E)-prop-1-enylphosphonodiamide 96 also underwent the RCM well. However, N,N’-dicinnamyl-vinylphosphonodiamides 94b,c (R’ = H, Me, R = Ph) always generated the corresponding N,N’-dicinnamyl-styrylphosphonodiamides 98 in 12–17% yields as byproducts via the RCM

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

• was stirred at room temperature for 12 h, then water (15 mL) was added to the mixture, and stirring was continued for 5 min. The reaction mixture was acidified with conc. HCl to pH 2 and extracted with DCM. The extract was washed with brine, dried over Na2SO4, and evaporated under reduced pressure

• ) at 0–5 °C a solution of KOH (0.392 g, 7 mmol) in H2O (1 mL) was added dropwise under stirring. The reaction mixture was stirred at this temperature for 1–4 h (in the case of ester 7 it was stirred at room temperature for 96 h), then acidified with conc. HCl to pH 5–6. The resultant precipitate was

• filtered. To the filtrate the corresponding ester 20–24 (1 mmol) was added. The reaction mixture was stirred at 0–5 °C for 1 h, then the solvent was removed under reduced pressure, the residue was dissolved in water, cooled to 0–5 °C and acidified with conc. HCl to pH 5–6. The resultant precipitate was

Post-synthesis from Lewis acid–base interaction: an alternative way to generate light and harvest triplet excitons

• Hengjia Liu and
• Guohua Xie

Beilstein J. Org. Chem. 2022, 18, 825–836, doi:10.3762/bjoc.18.83

• ), DPPPy-Ph-3F (17), and DPPPy-Ph-F (18, Figure 8), and determined the 11B NMR spectra (Figure 9c) [44]. When coordinated with nitrogen atoms, the resonance peak shifted slightly from ca. −10 to 0 ppm, which suggested the interaction between boron and nitrogen atoms. Wang’s group studied the interaction of

• )3 at different temperatures from 300 to 230 K. (c) 11B NMR spectra of B(C6F5)3, DPPPy-Py-F (compound 16)/B(C6F5)3, DPPPy-Ph-3F (compound 17)/B(C6F5)3, and DPPPy-Ph-F (compound 18)/B(C6F5)3 in CD2Cl2, respectively. Figure 9a and 9b were reprinted with permission from [43], Copyright 2011 American

Synthesis of α-(perfluoroalkylsulfonyl)propiophenones: a new set of reagents for the light-mediated perfluoroalkylation of aromatics

• Durbis J. Castillo-Pazos,
• Juan D. Lasso and
• Chao-Jun Li

Beilstein J. Org. Chem. 2022, 18, 788–795, doi:10.3762/bjoc.18.79

• synthetic chemistry, we report the synthesis of a series of bench-stable α-(perfluoroalkylsulfonyl)propiophenones. Their application as photocleavable reagents was tested with electron-rich aromatics under metal-free, redox- and pH-neutral conditions to enable late-stage perfluorooctylation

• halogenation reactions or oxidation. For these reasons, it would be ideal to develop an efficient methodology that allows for the generation of perfluoroalkyl radicals in a mild, redox- and pH-neutral manner, without the assistance of external photocatalysts, heavy metal catalysts, or further additives. Thus

• reactivity of these molecules allows this set of reagents to be both redox- and pH-neutral, while also being highly diversifiable. Additionally, all byproducts generated either during its synthesis or use in following reactions have the potential to be recycled, if so desired. Based on the fact that both

Synthesis of bis-spirocyclic derivatives of 3-azabicyclo[3.1.0]hexane via cyclopropene cycloadditions to the stable azomethine ylide derived from Ruhemann's purple

• Alexander S. Filatov,
• Olesya V. Khoroshilova,
• Anna G. Larina,
• Vitali M. Boitsov and
• Alexander V. Stepakov

Beilstein J. Org. Chem. 2022, 18, 769–780, doi:10.3762/bjoc.18.77

• asymmetric 1,3-dipolar cycloaddition of azomethine ylides and cyclopropenes catalyzed by a chiral Cu-(CH3CN)4BF4/Ph-Phosferrox complex for the construction of 3-azabicyclo[3.1.0]hexane derivatives [25]. Another concise enantioselective approach towards 3-azabicyclo[3.1.0]hexanes is based on a Cp*Ir-catalyzed

Synthesis of odorants in flow and their applications in perfumery

• Merlin Kleoff,
• Paul Kiler and
• Philipp Heretsch

Beilstein J. Org. Chem. 2022, 18, 754–768, doi:10.3762/bjoc.18.76

• %. Thus, Brenna and co-workers developed a cis-selective synthesis of 54 via a biocatalytic process in flow (Scheme 12) [45]. In the first step, a mixture of cyclohexanone 51, NADH, and isopropanol in an aqueous phosphate buffer (pH ≈ 7) is pumped through a continuously stirred membrane reactor at 30 °C

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

• membrane-like environment. Along these lines, no product formation was detectable when UbiA-297 was denaturated by heating prior to the assay (control), nor when a MenA-1335 (Maribacter sp. MS6) homolog was tested. Furthermore, different pH values and extended incubation times were investigated, however

• added to a final concentration of 0.1 mM. Cells were cultivated overnight at 16 °C before harvesting. Cultures were centrifuged, the cell pellet resuspended in Tris-HCl buffer (50 mM, pH 7.8) supplemented with dithiothreitol (DTT, 10 mM), and sonicated on ice (12 min, 100% C, 40% A, 2 seconds on and 3

• obtained protein pellet was resuspended in the same buffer as used for the bioassays. Protein concentration was measured according to Bradford [38]. Enzyme assays: All the enzyme assays were performed using a standard reaction mixture (100 µL) by adding 50 µL Tris-HCl (50 mM, pH 7.8) containing MgCl2, FPP

Shift of the reaction equilibrium at high pressure in the continuous synthesis of neuraminic acid

• Jannis A. Reich,
• Miriam Aßmann,
• Kristin Hölting,
• Paul Bubenheim,
• Jürgen Kuballa and
• Andreas Liese

Beilstein J. Org. Chem. 2022, 18, 567–579, doi:10.3762/bjoc.18.59

• parameters are listed in Table 5. Since Neu5Ac is acidic, 200 mM buffer solution with the addition of K2HPO4 was used to neutralize the solution to pH 7.2. Using the Haldane relation, the calculated equilibrium constants were 27 L/mol and 48 L/mol at 2 MPa and 115 MPa, respectively. Circulation reactor If

• (ECR8309F). For all immobilizations, a 20 mM sodium phosphate buffer with a pH of 7.4 was used as immobilization buffer. All filtration steps were executed using a membrane pump (Membrane pump ME 2C NT, Vacuubrandt GMBH & Co. KG, Wertheim, Germany) with bottle topper filter (Nalgene™, Thermo Fisher

• washed with immobilization buffer. For immobilization, the buffer of purified enzymes (150 mM imidazol, 300 mM NaCl, 50 mM sodium phosphate buffer pH 7.4) was exchanged to the immobilization buffer using ultracentrifuge units with 10 kDa Cut-off (Sartorius Vivaspin™, Göttingen, Germany). The unbuffered

Synthesis of a new water-soluble hexacarboxylated tribenzotriquinacene derivative and its competitive host–guest interaction for drug delivery

• Man-Ping Li,
• Nan Yang and
• Wen-Rong Xu

Beilstein J. Org. Chem. 2022, 18, 539–548, doi:10.3762/bjoc.18.56

• -containing amphiphile (trans-AZO) to produce the TBTQ-C6-trans-AZO supra-amphiphile by host–guest interactions in water. The supra-amphiphile was further self-assembled into photo and pH dual-responsive supramolecular vesicles that have a potential to serve as drug nanocarriers to enable controlled drug

• TBTQ-CB6DOX. Spermine (SM), an aliphatic polyamine overexpressed in some cancer cells, was expected to exhibit a higher binding affinity to the negatively charged TBTQ-CB6 host, because it exists mainly in a four positively charged form at physiological pH (about 7) [30][31]. Thus, SM was chosen as a

• (10 mL) of compound 2 (0.50 g, 0.36 mmol), 40% aqueous sodium hydroxide was added. The mixture was heated under reflux for 12 h. The solvent was removed by distillation and the residue was dissolved in water and the pH of the solution was adjusted to 2 with hydrochloric acid. The resulting precipitate

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

• for compounds with stronger CT emission (e.g., compounds 1 and 4). The phosphorescence (PH) spectra of the carbazole–pyrimidine TADF compounds were rather intriguing. 10 K PH spectra of compounds tCbz-mPYR, 1, 3, 5, and 6 clearly resembled that of individual tCbz units, peaking at about 418 nm [29

• ], while for the rest of the compounds the PH spectra were red-shifted, though still maintaining the vibronic structure. However, the closer inspection of the PH spectra, see Figure S29 in Supporting Information File 1, revealed that all PH spectra coincided with that of the tCbz unit. Actually, the lowest

Comparative study of thermally activated delayed fluorescent properties of donor–acceptor and donor–acceptor–donor architectures based on phenoxazine and dibenzo[a,j]phenazine

• Saika Izumi,
• Prasannamani Govindharaj,
• Anna Drewniak,
• Paola Zimmermann Crocomo,
• Satoshi Minakata,
• Leonardo Evaristo de Sousa,
• Piotr de Silva,
• Przemyslaw Data and
• Youhei Takeda

Beilstein J. Org. Chem. 2022, 18, 459–468, doi:10.3762/bjoc.18.48

• (Figure 2b), suggesting that these emissions have a mixed character of localized (1LE) and charge-transfer state (1CT, Figure 3b). The emission from the T1 state (phosphorescence, PH) at a low temperature (10 K) with the energy of ET1 = 2.26 eV showed a similar spectral shape to the phosphorescence

Synthesis of 3,4,5-trisubstituted isoxazoles in water via a [3 + 2]-cycloaddition of nitrile oxides and 1,3-diketones, β-ketoesters, or β-ketoamides

• Md Imran Hossain,
• Md Imdadul H. Khan,
• Seong Jong Kim and
• Hoang V. Le

Beilstein J. Org. Chem. 2022, 18, 446–458, doi:10.3762/bjoc.18.47

• phosphate buffer under weakly acidic conditions (pH 4.0) at room temperature for 15–24 h and generated 3,5-disubstituted isoxazolines and 3,4,5-trisubstituted isoxazoles in good yields (Figure 1) [28]. Notably, no metal catalysts were used in this method. The development of organic reactions in water not

• % methanol (Table 1, entry 15); in these cases, compound 4 was obtained in excellent yields (70% yield and 95% yield, respectively). Compound 4 was also formed almost exclusively in 76% yield when the reaction was run in phosphate buffer (pH 7.4) in the presence of 5% methanol with 10 mol % of DIPEA (Table 1

• corresponding ketone (10 mmol) in ethyl acetate (20 mL). The reaction mixture was stirred at rt for 12 h. After the reaction was complete, as indicated by TLC, the mixture was carefully treated with 10% aqueous NH4Cl (30 mL) and the pH adjusted to 5 with a solution of hydrochloric acid (3 M). The aqueous phase

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

• (2i)). Addition of water to the reaction mixture also reduces the pH of the medium and simultaneously increases the concentration of hydroxide ions, therefore, diphenoxyketones 5 were not produced and dihydroxyketones 8 were formed as side products in these cases. Among the approaches to produce α

Menadione: a platform and a target to valuable compounds synthesis

• Acácio S. de Souza,
• Ruan Carlos B. Ribeiro,
• Dora C. S. Costa,
• Fernanda P. Pauli,
• David R. Pinho,
• Matheus G. de Moraes,
• Fernando de C. da Silva,
• Luana da S. M. Forezi and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2022, 18, 381–419, doi:10.3762/bjoc.18.43

• ]. Different NbSBA-15 catalysts were evaluated and with the optimized reaction conditions, menadione (10) was synthetized in 100% conversion and 97.3% selectivity using NbSBA-15(2.2 pH) and H2O2 [69]. Sulman and co-workers, for instance, reported the synthesis of menadione (10) using supercritical (SC) carbon

Regioselectivity of the S_EAr-based cyclizations and S_EAr-terminated annulations of 3,5-unsubstituted, 4-substituted indoles

• Jonali Das and
• Sajal Kumar Das

Beilstein J. Org. Chem. 2022, 18, 293–302, doi:10.3762/bjoc.18.33

• substrates 20. Noteworthy is that substrates bearing an indolyl N–Ph or N–Boc moiety (instead of free indolyl N–H) failed to deliver the corresponding final cyclized products. The authors attributed this failure to the indole C3 position’s reduced nucleophilicity which thwarted the Michael addition step. In

New efficient synthesis of polysubstituted 3,4-dihydroquinazolines and 4H-3,1-benzothiazines through a Passerini/Staudinger/aza-Wittig/addition/nucleophilic substitution sequence

• Long Zhao,
• Mao-Lin Yang,
• Min Liu and
• Ming-Wu Ding

Beilstein J. Org. Chem. 2022, 18, 286–292, doi:10.3762/bjoc.18.32

• -azidobenzaldehyde (1a), benzoic acid (2a) and tert-butyl isocyanide (3a) as the reactants (Scheme 2). When a mixture of 1a, 2a, and 3a in CH2Cl2 was stirred at room temperature for 48 h, the three-component Passerini reaction was carried out smoothly and the azide 4a (R = Ph) was finally obtained in 87% yield

• isocyanates (Table 2, compounds 8a–l, R3 = Ph, 4-ClC6H4, 3-MeC6H4, 4-MeC6H4 and 4-CF3OC6H4) were used, good yields (69–86%) of the products were obtained, whereas moderate yields (54–57%) were obtained when the more steric secondary amines were utilized (Table 2, compound 8m and 8n, NR4R5 = N(Cy)2, N(iPr)2

• dialkylamines were utilized (Table 3, compounds 11l and 11m, NR4R5 = N(Cy)2, N(iPr)2). In cases when phenylmethylamine (compounds 11n and 11o, NR4R5 = N(Ph)Me) was used, 51–56% yields of the products were obtained, but when diphenylamine was used, no product was obtained (compound 11p, NR4R5 = NPh2). Conclusion

Recent developments and trends in the iron- and cobalt-catalyzed Sonogashira reactions

• Surendran Amrutha,
• Sankaran Radhika and
• Gopinathan Anilkumar

Beilstein J. Org. Chem. 2022, 18, 262–285, doi:10.3762/bjoc.18.31

• latter with salts of Pd(II) and Co(II) in ethylene glycol and water at pH 11 afforded the desired PdCo nanoparticles-3D graphene nanocomposite. The catalyst was then studied in the Sonogashira coupling reaction of arylacetylenes and aryl halides in the presence of various bases and solvents. The maximum

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

• were harvested by centrifugation (4,000g, 20 min), re-suspended in lysis buffer (20 Mm Tris/HCl, pH 8.0, EDTA-free protease inhibitor cocktail tablet, 0.02 mg/mL DNaseI). Cell lysis was performed by sonication on ice. Cells were exposed to Amplitude microns of ultrasound every 20 seconds for 10 minutes

• . The recombinant protein was separated from cell debris by centrifugation (20,000g, 30 min). The supernatant was loaded to a 5 mL HisTrapTM HP column (GE healthcare) pre-equilibrated with buffer A (50 mM Tris-HCl, pH 8.0, 150 mM NaCl, 20 mM imidazole) and purified at 4 °C using an ÄKTA pure FPLC system

• (GE Healthcare). The column was washed with buffer A to remove unbound proteins followed by elution of bound proteins with buffer B (50 mM Tris-HCl, pH 8.0, 150 mM NaCl, 500 mM imidazole). Further purification was carried out by gel filtration chromatography (Superdex S200 16/600 column, GE Healthcare

Synthesis and bioactivity of pyrrole-conjugated phosphopeptides

• Qiuxin Zhang,
• Weiyi Tan and
• Bing Xu

Beilstein J. Org. Chem. 2022, 18, 159–166, doi:10.3762/bjoc.18.17

• and 6b for 1, 2, and 3 days. A) TEM images of 1 before and after addition of ALP (0.5 U/mL) in PBS buffer (pH 7.4). Scale bar is 100 nm. Figure 3A was reprinted with permission from [62] https://pubs.acs.org/doi/10.1021/bm5010355, Copyright 2014 American Chemical Society. This content is not subjected

• to CC-BY 4.0. Permission requests related to the material excerpted should be directed to the ACS. B) TEM images of representative pyrrole-conjugated peptides 4a and 6b before and after the addition of ALP (1 U/mL) in PBS buffer (pH 7.4). Scale bar is 200 nm. Molecular structures of the parent

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

• under continuous stirring to a suspension of chitosan (5 g) in 100 mL of water. An ammonia solution was used to adjust the pH value of the mixture to 9. The solution was further stirred continuously overnight at room temperature. After that, the green catalyst was separated by filtration and dried under

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

• %, Tryptone (Difco Laboratories) 0.5%, dissolved in natural sea water (collected in Toyama Bay, Japan) The pH was adjusted to 7.3 before sterilization. The flasks were shaken at 30 °C for 2 days on a rotary shaker (200 rpm). The seed culture (3 mL) was transferred into 30 500 mL K-1 flasks each containing 100

• mL of A11M production medium (pH 7.0) consisting of 2.5% soluble starch, 0.2% glucose, 0.5% yeast extract, 0.5% Hipolypeptone (Wako Pure Chemical Industries, Ltd), NZ amine (Wako Pure Chemical Industries, Ltd), CaCO3 0.3%, and 1% Diaion HP-20 (Mitsubishi Chemical Co.) in natural sea water. The

1,2-Naphthoquinone-4-sulfonic acid salts in organic synthesis

• Ruan Carlos B. Ribeiro,
• Patricia G. Ferreira,
• Amanda de A. Borges,
• Luana da S. M. Forezi,
• Fernando de Carvalho da Silva and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2022, 18, 53–69, doi:10.3762/bjoc.18.5

• cleaner and form the substitution product at position C4. Fieser and Fieser were the first to study tautomerism between 4-arylamino-1,2-naphthoquinone A and 2-hydroxy-1,4-naphthoquinone-4-arylimine B (Scheme 3C) using the redox potential compared to the pH of the medium. It was observed that

• naphthoquinones A prevail in all pH regions except for extreme acidity, where there is a shift to the form of 2-hydroxy-1,4-naphthoquinone-4-arylimines [73][74]. However, in weakly acidic or alkaline solutions, A is the most stable tautomer (Scheme 3C) [75]. Fragoso and co-workers [76] studied the tautomeric

Stepwise PEG synthesis featuring deprotection and coupling in one pot

• Logan Mikesell,
• Dhananjani N. A. M. Eriyagama,
• Yipeng Yin,
• Bao-Yuan Lu and
• Shiyue Fang

Beilstein J. Org. Chem. 2021, 17, 2976–2982, doi:10.3762/bjoc.17.207

• using the expensive catalyst that was used in the literature [32] due to cost considerations. Another method we tried was to react excess TsO(PEG)4OTs with 2-phenylethan-1-ol under basic conditions to give 2 (Scheme 3). However, separation of 2 from TsO(PEG)4OTs and Ph(CH2)2O(PEG)4O(CH2)2Ph required

• convenience of the one-pot PEG elongation approach. The phenethyl group in 8 was removed with KHMDS and the intermediate alkoxide was reacted directly with 2 in one pot to give the (PEG)20 derivative 9. The same procedure was simply repeated to give PEG derivatives Ph(CH2)2O(PEG)28O(CH2)2Ph (10), Ph(CH2)2O

• (PEG)36O(CH2)2Ph (11), and Ph(CH2)2O(PEG)44O(CH2)2Ph (12). In the PEG elongation process, we used excess KHMDS (2.5 equiv) for the deprotection to overcome inadvertent moisture. To prevent the excess base from deprotecting the phenethyl groups in the monomer, before adding the monomer, the reaction