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

• synthesis, which include unidirectional iterative coupling, bidirectional iterative coupling, chain doubling, and chain tripling [15]. The base-labile protecting strategy can be easily incorporated into all those routes, and the routes can be shortened significantly by carrying out deprotection and coupling

• in one pot. We demonstrated the convenience of the one-pot PEG elongation approach using bidirectional iterative coupling route (Scheme 3). This route has the advantage of using the same monomer in each elongation cycle. In addition, the length of the monomer is significantly shorter than that of the

Chemical tuning of photoswitchable azobenzenes: a photopharmacological case study using nicotinic transmission

• Lorenzo Sansalone,
• Jun Zhao,
• Matthew T. Richers and
• Graham C. R. Ellis-Davies

Beilstein J. Org. Chem. 2019, 15, 2812–2821, doi:10.3762/bjoc.15.274

• . Keywords: acetylcholine receptors; bidirectional; photoswitchable drug; tetrafluoroazobenzene; visible light; Introduction Starting in 1937, azobenzenes (ABs) have attracted much attention because they undergo a photoreversible chemical transformation of the thermodynamically favored trans configuration

• decay is slow at 37 °C, frozen [14] such solutions could be used for many days without any change in pharmacological efficacy. Our final set of biological experiments with photochrome 2 examined its ability to work as a dynamic, bidirectional photoswitchable drug for nicotinic acetylcholine receptors

A combinatorial approach to improving the performance of azoarene photoswitches

• Joaquin Calbo,
• Aditya R. Thawani,
• Rosina S. L. Gibson,
• Andrew J. P. White and
• Matthew J. Fuchter

Beilstein J. Org. Chem. 2019, 15, 2753–2764, doi:10.3762/bjoc.15.266

• Supporting Information File 1. a) Tetra ortho-substituted azobenzenes represent a significant advance in terms of Z-isomer stability and completeness of photoswitching over azobenzene. b) Azoheteroarenes, developed by Fuchter and co-workers, offer quantitative, bidirectional photoswitching and long Z-isomer

Ultrafast processes triggered by one- and two-photon excitation of a photochromic and luminescent hydrazone

• Alessandro Iagatti,
• Baihao Shao,
• Alberto Credi,
• Barbara Ventura,
• Ivan Aprahamian and
• Mariangela Di Donato

Beilstein J. Org. Chem. 2019, 15, 2438–2446, doi:10.3762/bjoc.15.236

• stimulus, raise particular interest among the different classes of switches which have been developed to date. Light enables very specific spatial and temporal control of the switching event, allowing for selective response and bidirectional operation. It is thus not surprising that different classes of

Synthesis of (macro)heterocycles by consecutive/repetitive isocyanide-based multicomponent reactions

• Angélica de Fátima S. Barreto and
• Carlos Kleber Z. Andrade

Beilstein J. Org. Chem. 2019, 15, 906–930, doi:10.3762/bjoc.15.88

• [41] performed the first use of the diamine/diacid combination of bidirectional Ugi-MiBs in the synthesis of novel steroid–peptoid hybrid macrocycles. Scheme 25 shows two examples using this combination for the synthesis of cholane–peptoid hybrid macrocycles. Another application of the MiBs approach

• bidirectional macrocycles with exocyclic substituents with side chains derived from natural products [47]. The combination of acid components with side chains derived from natural products containing amino acid residues (e.g., Arg, Cys, His, Trp) and sugar, bifunctional components (diamino/diisocyanide) and

• macrocyclizations [44]. Synthesis of steroid–aryl hybrid cages by sequential 2- and 3-fold Ugi-4CR-based macrocyclizations [46]. Ugi-MiBs approach towards natural product-like macrocycles [47]. a) Bidirectional macrocyclization of peptides by double Ugi reaction. b) Ugi-4CR for the generation of exocyclic diversity

Oxidative and reductive cyclization in stiff dithienylethenes

• Michael Kleinwächter,
• Ellen Teichmann,
• Lutz Grubert,
• Martin Herder and
• Stefan Hecht

Beilstein J. Org. Chem. 2018, 14, 2812–2821, doi:10.3762/bjoc.14.259

• methylpyridinium group as a substituent on the photochromic unit [27][28][29]. However, by a combination of suitable substituents, a bidirectional system able to operate in both switching directions either electrochemically or photochemically has been reported [28]. We have recently developed a new subclass of

Facile synthesis of indolo[3,2-a]carbazoles via Pd-catalyzed twofold oxidative cyclization

• Chao Yang,
• Kai Lin,
• Lan Huang,
• Wei-dong Pan and
• Sheng Liu

Beilstein J. Org. Chem. 2016, 12, 2490–2494, doi:10.3762/bjoc.12.243

• ][12]. As an interest concerning the development of synthesis methods for carbazoles, we considered that indolo[3,2-a]carbazoles 1 which represents racemosin B and its analogues also could be conveniently delivered by bidirectional indole annulations from methyl 2,4-dianilinobenzoates 2 (Scheme 1

• -dianilinobenzoate (2f–p) with various substituents at the aniline moieties. Given the ease with which methyl 2,4-dianilinobenzoates could be assembled, further efforts were focused on the optimization studies of the key bidirectional indole annulations using 2a as the model substrate. To maximize efficiency and

The direct oxidative diene cyclization and related reactions in natural product synthesis

• Juliane Adrian,
• Leona J. Gross and
• Christian B. W. Stark

Beilstein J. Org. Chem. 2016, 12, 2104–2123, doi:10.3762/bjoc.12.200

• -mediated bidirectional oxidative cyclization approach [99]. Membranacin and membrarollin Membranacin (55) and membrarollin (62) are typical adjacent bis-THF acetogenins having a threo-cis-threo-cis-erythro configured core (Scheme 12 and Scheme 13). They were isolated from the seeds of the fruit tree

Stereodynamic tetrahydrobiisoindole “NU-BIPHEP(O)”s: functionalization, rotational barriers and non-covalent interactions

• Golo Storch,
• Sebastian Pallmann,
• Frank Rominger and
• Oliver Trapp

Beilstein J. Org. Chem. 2016, 12, 1453–1458, doi:10.3762/bjoc.12.141

• long as their chirality can be controlled by chiral additives or auxiliaries. In addition, the simultaneous presence of both axially chiral BIPHEP enantiomers can be beneficial as this allows bidirectional control of enantioselectivity depending on temperature [14][15]. In this approach, both product

Regulation of integrin and growth factor signaling in biomaterials for osteodifferentiation

• Qiang Wei,
• Theresa L. M. Pohl,
• Anja Seckinger,
• Joachim P. Spatz and
• Elisabetta A. Cavalcanti-Adam

Beilstein J. Org. Chem. 2015, 11, 773–783, doi:10.3762/bjoc.11.87

• receptors and result in optimal cell survival and migration signals. Growth factor-mediated activation of the receptors leads to clustering of integrins and activation of integrin signaling [8][17]. In a word, the crosstalk between integrins and growth factor receptors is bidirectional that integrins may

OligArch: A software tool to allow artificially expanded genetic information systems (AEGIS) to guide the autonomous self-assembly of long DNA constructs from multiple DNA single strands

• Kevin M. Bradley and
• Steven A. Benner

Beilstein J. Org. Chem. 2014, 10, 1826–1833, doi:10.3762/bjoc.10.192

• universal gas constant (1.987 cal/°C·mol) and ΔH and ΔS are the enthalpy and entropy of the base stacking adjusted for initiation factors [14], with ΔS also adjusted for salt concentrations using the formula [15]: AEGIS segments are designed using a bidirectional sliding-window approach. Starting at the

• that meets the above criteria. If no span can be created within the optimal window, the window is moved until an acceptable span can be created. With the bidirectional approach, the window moves 1 nt upstream from the optimal position, followed by 1 nt downstream, 2 nt upstream, 2 nt downstream, etc

Bidirectional cross metathesis and ring-closing metathesis/ring opening of a C₂-symmetric building block: a strategy for the synthesis of decanolide natural products

• Bernd Schmidt and
• Oliver Kunz

Beilstein J. Org. Chem. 2013, 9, 2544–2555, doi:10.3762/bjoc.9.289

• -membered ring lactones stagonolide E and curvulide A were synthesized using a bidirectional olefin-metathesis functionalization of the terminal double bonds. Key steps are (i) a site-selective cross metathesis, (ii) a highly diastereoselective extended tethered RCM to furnish a (Z,E)-configured dienyl

• ; natural products; ruthenium; Introduction Bidirectional synthesis through termini differentiation of meso, C2-symmetric or unsymmetric building blocks has emerged as an important strategy in natural product synthesis over the past two decades [1]. Early on, enantiomerically pure C2-symmetric compounds

A practical synthesis of long-chain iso-fatty acids (iso-C₁₂–C₁₉) and related natural products

• Mark B. Richardson and
• Spencer J. Williams

Beilstein J. Org. Chem. 2013, 9, 1807–1812, doi:10.3762/bjoc.9.210

• ][45][46], organomagnesium (sp2–sp3) [47], or organocopper (sp3–sp3) [48][49] cross-couplings; or (2) bidirectional extension of a central thiophene C4-fragment [50]. Two fundamentally different approaches worth special mention are the synthesis of the iso-C14 acid 3 by direct hydro-isopropylation of

The multicomponent approach to N-methyl peptides: total synthesis of antibacterial (–)-viridic acid and analogues

• Ricardo A. W. Neves Filho,
• Sebastian Stark,
• Bernhard Westermann and
• Ludger A. Wessjohann

Beilstein J. Org. Chem. 2012, 8, 2085–2090, doi:10.3762/bjoc.8.234

• a bidirectional sequence from the least- to the most-reactive amine (NMe-Val < H-Ant-OBn < H-Gly) to yield the protected tetrapeptide 2 (Scheme 1a). Alternatively, a multicomponent (MCR) approach based on a Ugi four-component reaction (Ugi-4CR) of dipeptide 3, isobutyraldehyde, methylamine and

• of stereochemistry. Retrosynthetic strategies for (−)-viridic acid (1) and analogues by (a) a bidirectional peptide-coupling sequence, and (b) a novel MCR approach. Reactions and conditions: (a) Boc-Gly-OH, EDCI, HOAt, TEA, CH2Cl2, rt, 20 h, 73%. (b) LiOH, THF/H2O (1:1), rt, 3 h, 97%. (c) Benzyl

Brønsted acid-promoted azide–olefin [3 + 2] cycloadditions for the preparation of contiguous aminopolyols: The importance of disiloxane ring size to a diastereoselective, bidirectional approach to zwittermicin A

• Hubert Muchalski,
• Ki Bum Hong and
• Jeffrey N. Johnston

Beilstein J. Org. Chem. 2010, 6, 1206–1210, doi:10.3762/bjoc.6.138

• diol. This development provides a basis for a stereocontrolled approach to the aminopolyol core of (−)-zwittermicin A using a bidirectional synthesis strategy. Keywords: azide; bidirectional synthesis; cycloaddition; dialkoxydisiloxane; TIPDS; triazoline; triflic acid; zwittermicin A; Introduction

• particularly intrigued by the possibility of a substrate controlled anti-diastereoselective azide–olefin reaction performed in a bidirectional fashion [13][14] to establish the requisite stereocenters of the C9–C15 C2 symmetric core of the natural product [11] as outlined in Scheme 1. Diastereoselective

• traditional 6-membered dialkoxysilane. The anti,anti-selectivity observed in this transformation provides a foundation for the straightforward preparation of the aminopolyol backbone of (−)-zwittermicin A using a bidirectional chain functionalization strategy. Retrosynthetic analysis outlining the

Polar tagging in the synthesis of monodisperse oligo(p-phenyleneethynylene)s and an update on the synthesis of oligoPPEs

• Dhananjaya Sahoo,
• Susanne Thiele,
• Miriam Schulte,
• Navid Ramezanian and
• Adelheid Godt

Beilstein J. Org. Chem. 2010, 6, No. 57, doi:10.3762/bjoc.6.57

• repeating unit. In the related bidirectional approach two repeating units are added in each coupling step (Scheme 1b) [25]. The divergent-convergent Moore–Tour-route (Scheme 2a) [26][27][28][29] which employs the diethyltriazenyl group to mask an iodo substituent [30][31]. 1-(Diethyltriazenyl)-4-(2

• molecules which very often have unbranched or slightly branched alkyl substituents present for solubility reasons. Synthesis of oligoPPEs by a unidirectional (a) or bidirectional (b) repeating unit by repeating unit approach. R denotes solubilising substituents. Three divergent-convergent routes to

Recent progress on the total synthesis of acetogenins from Annonaceae

• Nianguang Li,
• Zhihao Shi,
• Yuping Tang,
• Jianwei Chen and
• Xiang Li

Beilstein J. Org. Chem. 2008, 4, No. 48, doi:10.3762/bjoc.4.48

• double Sharpless AE/Sharpless AD. The building block 157 was then constructed through bidirectional chain synthesis strategy. The propargylic alcohol 159, obtained from 1,4-bis(alkenyloxy)benzene 158, was converted into butenolide 160 through Red-Al reduction, iodine treatment, and carbonylation

• ) (ED50 <10−12 µg/mL compared to adriamycin, ED50 = 1.76 × 10−2 µg/mL) [78][81]. In 1997, Marshall’s group reported the total synthesis of asiminocin (198) through a bidirectional approach starting from the (S,S)-tartrate derived dialdehyde 200 and the (R)-α-OSEM stannane 199 (Scheme 27) [82]. Addition of

• -metathesis played a key role (Scheme 39) [99]. The bis-THF core unit 289 was constructed through a bidirectional outside-in hydroxy mesylate cascade cyclization route from 288. The bisbutenolide analogue 292 was prepared from diene 290 and the butenolide segment 291 through Grubbs cross-metathesis. Reaction