Chemoenzymatic synthesis of the cardenolide rhodexin A and its aglycone sarmentogenin

• Fuzhen Song,
• Mengmeng Zheng,
• Dongkai Wang,
• Xudong Qu and
• Qianghui Zhou

Beilstein J. Org. Chem. 2025, 21, 2637–2644, doi:10.3762/bjoc.21.204

• hand, we first tried the synthesis of rhodexin A through direct glycosylation of 2 by the ʟ-rhamnose donor 2,3,4-tri-O-benzoyl-α-ʟ-rhamnopyranosyl trichloroacetimidate (14). However, the selective glycosylation at the C3-hydroxy group of 2 was a formidable challenge since competitive glycosylations of

Silica gel with covalently attached bambusuril macrocycle for dicyanoaurate sorption from water

• Michaela Šusterová and
• Vladimír Šindelář

Beilstein J. Org. Chem. 2025, 21, 2604–2611, doi:10.3762/bjoc.21.201

• report a new material, SG-NHCO-BU1, in which the BU1 macrocycle is covalently grafted onto the surface of silica gel. We demonstrate that this hybrid material can be used for the selective dicyanoaurate(I) sorption from water. Moreover, it is shown that unlike SG-BnBU, SG-NHCO-BU1 exhibits good stability

Visible-light-driven NHC and organophotoredox dual catalysis for the synthesis of carbonyl compounds

• Vasudevan Dhayalan

Beilstein J. Org. Chem. 2025, 21, 2584–2603, doi:10.3762/bjoc.21.200

• cycloalkanone scaffolds with potential applications in pharmaceutical and materials sciences (Scheme 12) [62]. Sumida, Ohmiya, and co-workers recently developed an NHC-and organic photoredox-catalyzed meta-selective Friedel–Crafts type acylation of electron-rich aromatic compounds 31. The described catalytic

• catalyst. The anticipated meta-acylation product 32 was achieved through highly selective C(sp3)–C(sp3)-radical–radical cross-coupling between the cyclohexadienyl radical C and the benzyl radical species F, formed via single-electron reduction. This photochemical method overturns the traditional ortho and

• /photoredox catalyzed borylacylation of alkenes. NHC-catalyzed oxidative functionalization of cinnamaldehyde. NHC/photocatalyzed oxidative Smiles rearrangement. NHC-catalyzed synthesis of cyclohexanones through photocatalyzed annulation. Dual organocatalyzed meta-selective acylation of electron-rich arenes

Recent advances in total synthesis of illisimonin A

• Juan Huang and
• Ming Yang

Beilstein J. Org. Chem. 2025, 21, 2571–2583, doi:10.3762/bjoc.21.199

• , which was subsequently subjected to a one-pot desilylation to afford 24. Reduction of both the ester and ketone functionalities in 24, followed by selective protection of the primary alcohol and re-oxidation of the secondary alcohol to ketone, furnished compound 25 in three steps. The ketone in 25 was

• % yield (63% brsm) or 50% yield after four cycles with recovery of starting material. Selective epoxidation of the isopropenyl group with m-CPBA delivered cyclization precursor 45 as an inseparable mixture of diastereomers (dr = 1:2.1). A Cp2TiCl-mediated cyclization of 45 constructed the tricyclo

• rearrangement only under Lewis acidic conditions to furnish 47. Selective TES deprotection with HF afforded Rychnovsky’s intermediate 29. (−)-Illisimonin A was obtained in 13% yield over the same 4-step sequence as reported by Rychnovsky’s group. An alternative 4-step endgame starting from 47 was also developed

Total syntheses of highly oxidative Ryania diterpenoids facilitated by innovations in synthetic strategies

• Zhi-Qi Cao,
• Jin-Bao Qiao and
• Yu-Ming Zhao

Beilstein J. Org. Chem. 2025, 21, 2553–2570, doi:10.3762/bjoc.21.198

• ryanodine (1) from ryanodol (4) – had long eluded chemists. The primary challenge involved the selective installation of the bulky pyrrole unit onto the sterically congested C3 secondary hydroxy group within a polyfunctionalized, polyhydroxylated framework. In 2016, building upon prior work, the Inoue group

• introduction of diverse substituents at the C2 position and precise modulation of oxidation states at other sites, including C3. The synthesis of 3-epi-ryanodol (5) commenced with compound 44. After the protection of the C10 secondary hydroxy group, a sterically controlled, face-selective reduction of the C3

• of (+)-ryanodol (4) in just 15 steps, highlighting the Pauson–Khand cyclization and a selenium dioxide-mediated selective oxidation as key transformations [48] (Scheme 7). To construct the multi-substituted five-membered ring in the target molecule, the authors strategically employed the Pauson–Khand

Ni-promoted reductive cyclization cascade enables a total synthesis of (+)-aglacin B

• Si-Chen Yao,
• Jing-Si Cao,
• Jian Xiao,
• Ya-Wen Wang and
• Yu Peng

Beilstein J. Org. Chem. 2025, 21, 2548–2552, doi:10.3762/bjoc.21.197

• followed by reaction with CH(OMe)3 afforded acetal 17, which was then subjected to a CH2Cl2 solution of TMSOTf and iPr2NEt. A mixture of enol methyl ethers 18 were thus produced by an elimination reaction. Eventually, a site-selective bromination of the double bond over the electron-rich benzene rings with

Synthesis and characterization of a isothiouronium-calix[4]arene derivative: self-assembly and anticancer activity

• Giuseppe Granata,
• Loredana Ferreri,
• Claudia Giovanna Leotta,
• Giovanni Mario Pitari and
• Grazia Maria Letizia Consoli

Beilstein J. Org. Chem. 2025, 21, 2535–2541, doi:10.3762/bjoc.21.195

• confirmed by comparison with the calix[4]arene precursor (1) lacking these functional units. The selective antiproliferative profile of compound 3 highlights its potential as a lead anticancer agent. Moreover, compound 3 holds promise for further development in combination multidrug therapy due to the

• mechanisms including elevation of reactive oxygen species (ROS) or interference with redox homeostasis, and inhibition of kinase or topoisomerase activities essential for cancer cell proliferation. The selective activity of thiouronium salts against cancer cells compared to non-malignant cells can be related

• discriminate between normal and cancer cells, as demonstrated by the calculated SI of 0.47. The high SI value by compound 3 evidenced the isothiouronium moieties retain the selective cytotoxicity towards cancer cells also when tethered to the calixarene scaffold. Since the long alkyl chains in compound 3 could

Isoorotamide-based peptide nucleic acid nucleobases with extended linkers aimed at distal base recognition of adenosine in double helical RNA

• Grant D. Walby,
• Brandon R. Tessier,
• Tristan L. Mabee,
• Jennah M. Hoke,
• Hallie M. Bleam,
• Angelina Giglio-Tos,
• Emily E. Harding,
• Vladislavs Baskevics,
• Martins Katkevics,
• Eriks Rozners and
• James A. MacKay

Beilstein J. Org. Chem. 2025, 21, 2513–2523, doi:10.3762/bjoc.21.193

• acid (RNA) impacts many biological processes; however, the complexities of its many roles are not completely understood. Therefore, designing tools for molecular recognition is of paramount importance. Peptide nucleic acids (PNA) show promise as a tool for selective recognition of double helical

• than 10 times stronger to RNA than to DNA [19]. Since the seminal report, much work has focused on exploring synthetic nucleobases in efforts to develop tools for sequence selective recognition of any RNA [13]. Figure 1 shows several of the most common monocyclic nucleobases used for each of the four

• monomer. We reported a similar result for 5-triazolyluracil [28]. However, despite the development of pyrimidine-recognizing bases (P, P9, E, etc.), the sequence selective recognition of any double helical region of RNA remains an elusive problem owing to the difficulties in pyrimidine recognition via a

Palladium-catalyzed regioselective C1-selective nitration of carbazoles

• Vikash Kumar,
• Jyothis Dharaniyedath,
• Aiswarya T P,
• Sk Ariyan,
• Chitrothu Venkatesh and
• Parthasarathy Gandeepan

Beilstein J. Org. Chem. 2025, 21, 2479–2488, doi:10.3762/bjoc.21.190

• valuable platform for the selective functionalization of carbazoles, offering potential applications in optoelectronics, functional organic materials, and related areas while contributing to the advancement of C–H activation methodologies. Keywords: C–H activation; carbazole; catalysis; nitration

• nitration of carbazole is highly desirable [68][69]. In this context, we envisioned utilizing a directing group-assisted regioselective C–H activation strategy to achieve the C1-selective nitration of carbazole. Through our efforts, we identified a palladium-catalyzed reaction system for C1 nitration of

• ). Plausible catalytic cycle. (a) Representative examples of bioactive nitrocarbazoles. (b) Traditional electrophilic aromatic substitution approach for the nitration of carbazole. (c) Present work: palladium-catalyzed directed C1-selective nitration reaction. Effect of directing groups on the nitration of the

Transformation of the cyclohexane ring to the cyclopentane fragment of biologically active compounds

• Natalya Akhmetdinova,
• Ilgiz Biktagirov and
• Liliya Kh. Faizullina

Beilstein J. Org. Chem. 2025, 21, 2416–2446, doi:10.3762/bjoc.21.185

• available (+)-sclareolide (101) as starting compound, from which key alcohol 102 was synthesized in 7 steps. Selective mesylation of the secondary alcohol in 102 followed by semipinacol rearrangement catalyzed by t-BuOK afforded diketone 104 as a pair of epimers at C12 in a 1:1 ratio, with 70% overall yield

• -dihydronaphthalenes. Silva et al. have also developed an effective method for the stereoselective oxidation of tetralone derivatives using chiral hypervalent iodine reagents [61][62]. Hypervalent iodine compounds are widely used in organic synthesis as selective oxidants and enantiomerically pure reagents. In terms

• 2012, Lin and co-workers [69] isolated the membrane diterpenoid (−)-134 from the marine soft coral Sinularia pavida. The study showed that (−)-134 exhibits highly selective inhibition against the human promyelocytic leukemia cell line HL-60 with an IC50 of 2.7 μg/mL. Structurally, (−)-134 contains a

Synthetic study toward vibralactone

• Liang Shi,
• Jiayi Song,
• Yiqing Li,
• Jia-Chen Li,
• Shuqi Li,
• Li Ren,
• Zhi-Yun Liu and
• Hong-Dong Hao

Beilstein J. Org. Chem. 2025, 21, 2376–2382, doi:10.3762/bjoc.21.182

• moiety have been isolated and demonstrate potent bioactivities [7] (Figure 1). For example, lactacystin (1) which was isolated by Ōmura and co-workers [8][9], is a potent and selective proteasome inhibitor; its active form is the synthetic precursor omuralide (2) [10][11]. Similarly, salinosporamide (3

Conformational effects on iodide binding: a comparative study of flexible and rigid carbazole macrocyclic analogs

• Guang-Wei Zhang,
• Yong Zhang,
• Le Shi,
• Chuang Gao,
• Hong-Yu Li and
• Lei Xue

Beilstein J. Org. Chem. 2025, 21, 2369–2375, doi:10.3762/bjoc.21.181

• selective recognition. Balancing binding affinity and selectivity through precise conformational engineering remains a critical challenge [11]. Previous studies, such as those by Tian et al. [12], demonstrated selective binding in chiral assemblies via crown ether chain-length modulation. The dynamic

• by enabling dynamic host–guest complementarity. Such insights are critical for designing adaptive receptors for applications like environmental sensing or selective ion extraction. Conclusion In summary, two carbazole-based macrocyclic structural analogs (PBG and WDG) were synthesized via a

Rotaxanes with integrated photoswitches: design principles, functional behavior, and emerging applications

• Jullyane Emi Matsushima,
• Khushbu,
• Zuliah Abdulsalam,
• Udyogi Navodya Kulathilaka Conthagamage and
• Víctor García-López

Beilstein J. Org. Chem. 2025, 21, 2345–2366, doi:10.3762/bjoc.21.179

• form selective hydrogen bonds between the carbonyl oxygen of the fumaramide unit and the N–H groups of benzylic amide rings. Upon isomerization to the cis isomer, the hydrogen-bonding interactions are weakened, enabling the macrocycle to migrate to a second recognition station [61]. Despite their

• selective detection of sulfite for potential biological applications. Furthermore, the same group reported a photoswitchable [2]rotaxane containing a spiropyran stopper and a macrocycle armed with tetraphenylethylene for photopatterning applications (Figure 11) [20]. The macrocycle has been shown to shuttle

Comparative analysis of complanadine A total syntheses

• Reem Al-Ahmad and
• Mingji Dai

Beilstein J. Org. Chem. 2025, 21, 2334–2344, doi:10.3762/bjoc.21.178

• receptor (GPCR) X2 (MrgprX2), which is highly expressed in neurons and functions as a modulator of pain. Complanadine A serves as a selective agonist of MrgprX2. Structurally, complanadine A is an unsymmetrical dimer of the tetracyclic lycodine (5) via a C2–C3’ linkage [9][10]. Complanadine B is a mono

• , followed by acetylation of the resulting propargylic alcohol afforded 17 which was further advanced to 18 via copper-catalyzed selective displacement of the propargyl acetate with benzylamine and hydrolysis of the primary acetate. The primary alcohol of 18 was activated with PPh3/CCl4, triggering an

• synthetic route enabled Siegel and co-workers to determine the first biological target of complanadine A. Screening against a panel of cell surface GPCRs revealed that complanadine A acts as a selective agonist of MrgprX2, while the monomer lycodine showed no significant activity towards this target. This

Recent advances in Norrish–Yang cyclization and dicarbonyl photoredox reactions for natural product synthesis

• Peng-Xi Luo,
• Jin-Xuan Yang,
• Shao-Min Fu and
• Bo Liu

Beilstein J. Org. Chem. 2025, 21, 2315–2333, doi:10.3762/bjoc.21.177

• favor Norrish–Yang cyclization over the competing unproductive Norrish type II fragmentation pathway; (2) the long excitation wavelength of 1,2-diketones (λmax ≈ 450 nm) enables their selective activation in the presence of other photochemically excitable groups [5][6]. Furthermore, the resulting α

• C5–C6 bond) was subjected to Norrish–Yang cyclization conditions (Scheme 5b), the two methyl groups at C4 initially underwent non-selective 1,5-HAT, resulting in a loss of both regio- and stereoselectivity. In both cases, the functional groups on the ring E likely exert a significant influence on the

• (44) would trigger a quinone-based Norrish–Yang cyclization, enabling divergent synthesis of these meroterpenoids (or their core structures). In Yang's divergent total synthesis, Wieland–Miescher ketone (18) served as the starting material. Selective acetalization of the non-conjugated ketone in 18

Insoluble methylene-bridged glycoluril dimers as sequestrants for dyes

• Suvenika Perera,
• Peter Y. Zavalij and
• Lyle Isaacs

Beilstein J. Org. Chem. 2025, 21, 2302–2314, doi:10.3762/bjoc.21.176

• found that the water-soluble naphthalene-walled glycoluril dimer G2M2 (Figure 1) – with its roughly co-planar aromatic walls – is selective for planar aromatic cations as guests [38]. In order the complement the tricyclic ring system present in the panel of dyes (Figure 2), we envisioned the use of even

Halogenated butyrolactones from the biomass-derived synthon levoglucosenone

• Johannes Puschnig,
• Martyn Jevric and
• Ben W. Greatrex

Beilstein J. Org. Chem. 2025, 21, 2297–2301, doi:10.3762/bjoc.21.175

• epoxidations of 5 are highly stereoselective [44]. Unambiguous assignment of configuration for the diastereomers was not possible on the basis of the selective 1D NOE spectra due to the lack of informative crosspeaks. Limiting the amount of oxidant (H2O2 or peracetic acid) resulted in mixtures, suggesting that

Enantioselective radical chemistry: a bright future ahead

• Anna C. Renner,
• Sagar S. Thorat,
• Hariharaputhiran Subramanian and
• Mukund P. Sibi

Beilstein J. Org. Chem. 2025, 21, 2283–2296, doi:10.3762/bjoc.21.174

• selective synthesis owing to their unprecedented catalytic activity and selectivity. Advances in the field of protein engineering have made enzymatic catalysis more amenable to enantioselective organic synthesis in the past decade. Recent advances in the development of synergistic catalytic systems

• products with a new all-carbon quaternary stereocenter (Scheme 11) [86]. With a Ni(II)–bisoxazoline complex as the catalyst, various substrates underwent the transformation with good to high yields and high enantioselectivities. The reactions were regioselective, resulting in the selective

• functionalization of the terminal carbon atom of the silyl polyenolate. In the reaction of silyl tetraenol ether 47, selective reaction at the η position occurred, and the product 48 was obtained in 78% yield and 96% ee. Conclusion This perspective highlights important contributions in the area of enantioselective

Pathway economy in cyclization of 1,n-enynes

• Hezhen Han,
• Wenjie Mao,
• Bin Lin,
• Maosheng Cheng,
• Lu Yang and
• Yongxiang Liu

Beilstein J. Org. Chem. 2025, 21, 2260–2282, doi:10.3762/bjoc.21.173

• regulatory role in chemical transformations, exerting kinetic modulation through solvation effects on activation barriers and reaction rates, dictating thermodynamic equilibria that govern product distribution, and enabling precise reaction pathway regulation via selective stabilization of critical

• solvent-controlled selective syntheses of two polycyclic compounds (Scheme 6) [13]. Using PdCl2 as the catalyst and DMF as the solvent, substrate 22 underwent a 6-endo-dig cyclization and subsequent enone insertion, forming a palladium–carbon bond intermediate. Protonolysis yielded isocoumarin-fused

• cyclization and subsequent deprotonation furnished 1,3-disubstituted or 1,2,3-trisubstituted naphthalenes 29 (Scheme 7, path a). When the alkyne terminus was iodo-substituted or unsubstituted, the 5-exo-dig cyclization pathway proceeded via selective activation of the iodoalkyne, generating 1-methyleneindene

Research towards selective inhibition of the CLK3 kinase

• Vinay Kumar Singh,
• Frédéric Justaud,
• Dabbugoddu Brahmaiah,
• Nangunoori Sampath Kumar,
• Blandine Baratte,
• Thomas Robert,
• Stéphane Bach,
• Chada Raji Reddy,
• Nicolas Levoin and
• René L. Grée

Beilstein J. Org. Chem. 2025, 21, 2250–2259, doi:10.3762/bjoc.21.172

• splicing process. Among the four isoforms of CLKs, CLK3 is the one for which the biological roles are less understood, in part because no selective inhibitor of this challenging kinase has been found to date. Based on structural analysis of the CLKs we have identified the lysine 241, present only in CLK3

• kinases” because of the lack of functional annotations and high-quality molecular probes for functional investigations [7][8]. Thus, new studies are still required for the discovery of selective inhibitors for each of these kinases in order to better clarify their mechanisms of action and their roles in

• that no potent and selective inhibitor of this specific kinase has been reported, to the best of our knowledge. Among the Tchem kinase inhibitors [9], only four molecules demonstrated significant enzymatic inhibition of CLK3 (from 6.5 nM to 110 nM, Table 1, [10]): SM08502, T-025, T3, and CX-4945

Pd-catalyzed dehydrogenative arylation of arylhydrazines to access non-symmetric azobenzenes, including tetra-ortho derivatives

• Loris Geminiani,
• Kathrin Junge,
• Matthias Beller and
• Jean-François Soulé

Beilstein J. Org. Chem. 2025, 21, 2234–2242, doi:10.3762/bjoc.21.170

• sterically tuned substrates promotes selective N-arylation at the terminal nitrogen. The protocol tolerates a wide range of functional groups and enables the synthesis of well-decorated azobenzenes, including tetra-ortho-substituted derivatives. Notably, the reaction proceeds under an O2 atmosphere and in

• (OAc)₂/BINAP catalytic system [51], which enabled selective C–N coupling at the terminal nitrogen and suppressed denitrogenative by-products [52][53][54]. Although the general strategy is similar, our method uses the [PdCl(C3H5)]2/t-BuXPhos catalytic system, which provided higher yields and broader

• t-BuXPhos to promote selective C–N-bond formation. This approach makes use of commercially available starting materials and displays broad functional group tolerance. Notably, it enables access to sterically demanding tetra-ortho-substituted azobenzenes in moderate to good yields. The results

Thiadiazino-indole, thiadiazino-carbazole and benzothiadiazino-carbazole dioxides: synthesis, physicochemical and early ADME characterization of representatives of new tri-, tetra- and pentacyclic ring systems and their intermediates

• Gyöngyvér Pusztai,
• László Poszávácz,
• Anna Vincze,
• András Marton,
• Ahmed Qasim Abdulhussein,
• Judit Halász,
• András Dancsó,
• Gyula Simig,
• György Tibor Balogh and
• Balázs Volk

Beilstein J. Org. Chem. 2025, 21, 2220–2233, doi:10.3762/bjoc.21.169

• spatial proximities obtained from either NOESY or ROESY NMR measurements. The NH moiety is close to N=CH in the (E) isomer, while NH is close to CH2 in the (Z) isomer. As an example, in case of hydrazone 7h, a selective 1D NOESY spectrum was recorded with the excitation of NH (Figure 2 and Figure 3). In

• both Figures, beside the selective 1D NOESY spectrum (upper part in Figure 2 and Figure 3), the 1H NMR spectrum (lower part) is also presented. The spatial proximity of NH with N=CH (marked with a red arrow in Figure 2) or with CH2 (red arrow in Figure 3) proves the (E) or (Z) configuration of the N=C

• ), 128.8 (2C), 126.4, 123.6, 121.2, 118.1, 116.4, 111.8, 35.0, 9.3; IR (KBr) ν̃: 3377, 1354, 1292, 1137, 1084, 694 cm−1; HREIMS (m/z): [M•]+ calcd for C17H15N3O2S, 325.0885; found, 325.0886. Phthalazinones 1, benzothiadiazine dioxides 2, and thiadiazinoindole dioxides 3. 1H NMR and selective 1D NOESY (with

Electrochemical cyclization of alkynes to construct five-membered nitrogen-heterocyclic rings

• Lifen Peng,
• Ting Wang,
• Zhiwen Yuan,
• Bin Li,
• Zilong Tang,
• Xirong Liu,
• Hui Li,
• Guofang Jiang,
• Chunling Zeng,
• Henry N. C. Wong and
• Xiao-Shui Peng

Beilstein J. Org. Chem. 2025, 21, 2173–2201, doi:10.3762/bjoc.21.166

• afforded 12a and regenerated (DMSO)nCuI. Notably, this reaction, using KI as the only additive and performing under ambient conditions in a non-volatile aqueous solvent, was a simple, selective, efficient and sustainable electrosynthesis of indole derivatives. 3-Selenylindoles were also formed by

C2 to C6 biobased carbonyl platforms for fine chemistry

• Jingjing Jiang,
• Muhammad Noman Haider Tariq,
• Florence Popowycz,
• Yanlong Gu and
• Yves Queneau

Beilstein J. Org. Chem. 2025, 21, 2103–2172, doi:10.3762/bjoc.21.165

•  12) [43]. Many other studies have concerned lactic acid (LA) because of its low cost and versatile reactivity owing to the presence of one hydroxy group and one carboxylic group. Zhou et al. [44] summarized the selective catalytic (chemical or biological) pathways for the conversion of lactic acid

• -synthesis of formamides and formates was achieved in particularly good yield by selective oxidation of DHA using a Cu/Al2O3 catalyst with single active CuII species at room temperature without using a base (Scheme 20). 1-Hydroxypropan-2-one Gu et al. reported the [3 + 2] cyclization reaction of 1

• such as bagasse, corncobs, stalks, switchgrass and hardwoods [156][157][158][159][160][161][162], thanks to preliminary selective dissolution and depolymerization of hemicellulose into pentose sugars. Deep eutectic solvents were recently shown to allow fractionation of lignin and production of furfural

The application of desymmetric enantioselective reduction of cyclic 1,3-dicarbonyl compounds in the total synthesis of terpenoid and alkaloid natural products

• Dong-Xing Tan and
• Fu-She Han

Beilstein J. Org. Chem. 2025, 21, 2085–2102, doi:10.3762/bjoc.21.164

• to ketone 48 via a seven-step transformation. Finally, removal of the TBS group in 48 followed by a sequential reduction and selective oxidation of allylic primary alcohol achieved the total synthesis of (−)-cyrneine A (7). The authors then moved forward to the synthesis of other target molecules

• (Scheme 3) [31][32]. Oxidation state adjustment of 48 led to the ketone 49. Starting from this common intermediate, firstly, base-promoted double bond migration and oxidation at the γ-position gave tertiary alcohol 50. Deprotection of acetyl in 50 followed by selective oxidation delivered (−)-cyrneine B

• (9). Secondly, a based-mediated concomitant double bond migration and deacetylation, and selective oxidation of allylic primary alcohol accomplished the total synthesis of (−)-glaucopine C (10). On the other hand, Barton–McCombie deoxygenation and isopropylation of 43 produced ketone 52. Subsequently