Bromination of endo-7-norbornene derivatives revisited: failure of a computational NMR method in elucidating the configuration of an organic structure

• Demet Demirci Gültekin,
• Arif Daştan,
• Yavuz Taşkesenligil,
• Cavit Kazaz,
• Yunus Zorlu and
• Metin Balci

Beilstein J. Org. Chem. 2023, 19, 764–770, doi:10.3762/bjoc.19.56

• in terms of neighboring group participation by the bromine atom in the methano bridge (8→9). Thus, backside attack of the bromine atom on C7 in 8 at C2 of the three-membered bromonium ion can lead to the four-membered bromonium ion 9. Attack of bromide ion at C-3 of 9 furnishes the cis-addition

Synthetic strategies toward 1,3-oxathiolane nucleoside analogues

• Umesh P. Aher,
• Dhananjai Srivastava,
• Girij P. Singh and
• Jayashree B. S

Beilstein J. Org. Chem. 2021, 17, 2680–2715, doi:10.3762/bjoc.17.182

• introduction on important classical approaches and older yet creative methods to provide the reader with a historical context. For comparison, this will be followed by a discussion of more modern techniques, including chiral auxiliaries for neighboring group participation and transition metal-catalyzed

Progress and challenges in the synthesis of sequence controlled polysaccharides

• Giulio Fittolani,
• Theodore Tyrikos-Ergas,
• Denisa Vargová,
• Manishkumar A. Chaube and
• Martina Delbianco

Beilstein J. Org. Chem. 2021, 17, 1981–2025, doi:10.3762/bjoc.17.129

• -mannosides is conventionally achieved with [142][157][269], or even without [270], neighboring group participation (e.g., Ac, Bz). The favorable anomeric effect ensures efficient glycosylation reactions. The synthesis of α-mannosides is widely established, allowing the chemical synthesis of the longest

CF₃-substituted carbocations: underexploited intermediates with great potential in modern synthetic chemistry

• Anthony J. Fernandes,
• Armen Panossian,
• Bastien Michelet,
• Agnès Martin-Mingot,
• Frédéric R. Leroux and
• Sébastien Thibaudeau

Beilstein J. Org. Chem. 2021, 17, 343–378, doi:10.3762/bjoc.17.32

SnCl₄-catalyzed solvent-free acetolysis of 2,7-anhydrosialic acid derivatives

• Kesatebrhan Haile Asressu and
• Cheng-Chung Wang

Beilstein J. Org. Chem. 2019, 15, 2990–2999, doi:10.3762/bjoc.15.295

• destabilizing electron-withdrawing carboxy group flanking atom C-2 and the lack of a participating auxiliary in position C-3 of 5. Glycal 24 is widely used for α-sialylation by utilizing neighboring group participation and site-selective fluorination at C-3 [12][13][14][41]. Moreover, it is the main precursor

Iodine-mediated hydration of alkynes on keto-functionalized scaffolds: mechanistic insight and the regiospecific hydration of internal alkynes

• Zachary Lee,
• Brandon R. Jones,
• Nyochembeng Nkengbeza,
• Michael Phillips,
• Kayla Valentine,
• Alexis Stewart,
• Brandon Sellers,
• Nicholas Shuber and
• Karelle S. Aiken

Beilstein J. Org. Chem. 2019, 15, 2747–2752, doi:10.3762/bjoc.15.265

• through a 5-exo-dig neighboring group participation (NGP) cyclization and an α-iodo intermediate. The work described herein probes the existence of the intermediate through NMR investigations and explores the scope of the hydration process with internal alkynes. The NMR experiments confirm the existence

• of the α-iodo intermediate, and methodology studies demonstrate that alkyl-capped, asymmetric, internal alkynes undergo a regiospecific hydration, also via the 5-exo-dig NGP pathway. Keywords: α-iodo intermediate; internal alkyne; iodine-mediated hydration; neighboring group participation

• , internal alkynes results in a mixture of regioisomers [20][23][24]. Moreover, per Baldwin’s rules, with neighboring group participation, a 5-exo-dig (via 13 and 14) or 6-endo-dig pathway (via 16 and 17), or both, are possible outcomes for such alkynes [25]. The 5-exo-dig route would provide 15, while the 6

D-Fructose-based spiro-fused PHOX ligands: synthesis and application in enantioselective allylic alkylation

• Michael R. Imrich,
• Jochen Kraft,
• Cäcilia Maichle-Mössmer and
• Thomas Ziegler

Beilstein J. Org. Chem. 2018, 14, 2082–2089, doi:10.3762/bjoc.14.182

• group participation in conformer 9b leads to the same anomer as predicted by the Fürst–Plattner rule. Neighboring group participation provides an alternative explanation for the already mentioned longer reaction times for the acylated sugars 7j–m. Because of the high delocalization of the positive

• conformers 9a and 9b. Neighboring group participation of ester protective groups. For better clarity C-2 is not shown in conformers 9a and 9c. Pd catalyzed Tsuji–Trost reation. BSA: N,O-bis(trimethylsilyl)acetamide, DMM: dimethyl malonate. Synthesis of spiro-fused oxazolines 10 and 11 via Ritter reaction

• is such a substituent the oxocarbenium ion 9a is stabilized as indicated in Scheme 6. In the stabilized species 9c the formerly favored nucleophilic attack from the top is blocked so that the addition of the nitrile has to occur from the bottom and higher amounts of 11 are generated. Neighboring

Enzyme-free genetic copying of DNA and RNA sequences

• Marilyne Sosson and
• Clemens Richert

Beilstein J. Org. Chem. 2018, 14, 603–617, doi:10.3762/bjoc.14.47

• crystallization. We note that the neighboring group participation proposed should be limited to leaving groups with a second nucleophilic site at the appropriate position. Other leaving groups than methylimidazole should not be able to react via the same dominant reaction pathway. In our hands, compounds with a

Strategies toward protecting group-free glycosylation through selective activation of the anomeric center

• A. Michael Downey and
• Michal Hocek

Beilstein J. Org. Chem. 2017, 13, 1239–1279, doi:10.3762/bjoc.13.123

• of this chemistry is its ability to provide 1,2-cis glycosides with good stereoselectivity, as these glycosides still remain among the most challenging stereoisomers to synthesize as C2 neighboring group participation is not possible [40]. In fact, the access to 1,2-cis glycosides is considered a

• electrophilic carbon adjacent to the oxocarbenium ion then reacts with the nucleophilic acceptor in either and SN1 or SN2-like mechanism depending on the chemical stability of the glycosyl cation [53]. The stereochemical outcome of the reaction is generally dictated either by neighboring-group participation of

• position 2 on the ring or by the anomeric effect when neighboring group participation is not possible [54][55]. Seemingly impossible Lewis acid-mediated processes are then available for the other hydroxy groups on the unprotect donor molecule and some examples are highlighted below. 3.3.1 Access of 1,2-cis

Total synthesis of TMG-chitotriomycin based on an automated electrochemical assembly of a disaccharide building block

• Yuta Isoda,
• Norihiko Sasaki,
• Kei Kitamura,
• Shuji Takahashi,
• Sujit Manmode,
• Naoko Takeda-Okuda,
• Jun-ichi Tamura,
• Toshiki Nokami and
• Toshiyuki Itoh

Beilstein J. Org. Chem. 2017, 13, 919–924, doi:10.3762/bjoc.13.93

• lack of neighboring group participation [27]. 4-Fluorophenyl 3,4,6-tri-O-acetyl-2-deoxy-2-azido-β-D-thioglucoside (2a) afforded the corresponding disaccharide α-isomer 5aα exclusively by the reaction with building block 4 via the glycosyl triflate intermediate 3a (Scheme 1). On the other hand, 4

First total synthesis of kipukasin A

• Chuang Li,
• Haixin Ding,
• Zhizhong Ruan,
• Yirong Zhou and
• Qiang Xiao

Beilstein J. Org. Chem. 2017, 13, 855–862, doi:10.3762/bjoc.13.86

• ). Kipukasin A could be constructed by Vorbrüggen glycosylation [22][23] of a properly protected glycosyl donor 3 with uracil (4). Neighboring group participation of the 2’-O-acetyl group stereoselectively facilitate the β-glycosidic bond formation. Thus, the choice of a suitable protecting group at 5-OH

Silyl-protective groups influencing the reactivity and selectivity in glycosylations

• Mikael Bols and
• Christian Marcus Pedersen

Beilstein J. Org. Chem. 2017, 13, 93–105, doi:10.3762/bjoc.13.12

• been applied to prepare partially acylated cholestan glycosides. In this case an imidate with a 2-O-acetate and 3,4-O-TES protection was used, which ensured stereoselectivity by neighboring-group participation [11]. For similar reasons the per-TES-protected thioglycoside 7 was employed to prepare the

• -controlled glucuronylation, where the bulky silylene in 75 ensures high selectivity without neighboring group participation (Scheme 16) [67]. Conclusion Much indicates that glycosyl donors with silyl protective groups generally are more reactive than their alkylated counterparts presumably due to the O-silyl

Multivalent scaffolds induce galectin-3 aggregation into nanoparticles

• Candace K. Goodman,
• Mark L. Wolfenden,
• Pratima Nangia-Makker,
• Anna K. Michel,
• Avraham Raz and
• Mary J. Cloninger

Beilstein J. Org. Chem. 2014, 10, 1570–1577, doi:10.3762/bjoc.10.162

• group participation of the 2-O-acetyl protecting group, afforded the desired anomers in good yields. The trichloroacetimidate intermediate was formed to enhance coupling. Syntheses of the carbohydrate-functionalized dendrimers were performed by addition of compound 1 as shown in Scheme 2. The

• and biological phenomena [27][28]. In this investigation, PAMAM dendrimers were functionalized using a methodology similar to previous literature [29]. Synthesis of β-lactoside derivative 1 was performed as shown in Scheme 1. Lewis acid facilitated glycosylation, which was directed by neighboring

Functionalization of anthracene: A selective route to brominated 1,4-anthraquinones

• Kiymet Berkil Akar,
• Osman Cakmak,
• Orhan Büyükgüngör and
• Ertan Sahin

Beilstein J. Org. Chem. 2011, 7, 1036–1045, doi:10.3762/bjoc.7.118

• multiplet at δ 7.71. Finally, X-ray analysis of the compound was performed and the exact configuration was proved to be dihydroxy 17 (Figure 2). The stereoselective formation of 17 can be explained by the neighboring-group participation, as shown in Scheme 4. We assume that cis orientation of bromine atoms

Study of thioglycosylation in ionic liquids

• Jianguo Zhang and
• Arthur Ragauskas

Beilstein J. Org. Chem. 2006, 2, No. 12, doi:10.1186/1860-5397-2-12

• nature of the protecting group on the C2-hydroxyl. Neighboring group participation of the C2 blocking group can be used to ensure a very high degree of stereoselectivity for the glycosylation reaction.[17] Herein, we wish to report the synthesis of alkyl glycosides or disaccharides employing 1-butyl-3