Preactivation-based chemoselective glycosylations: A powerful strategy for oligosaccharide assembly

• Weizhun Yang,
• Bo Yang,
• Sherif Ramadan and
• Xuefei Huang

Beilstein J. Org. Chem. 2017, 13, 2094–2114, doi:10.3762/bjoc.13.207

• acid synthesis. With continuous development, the preactivation strategy will achieve wider applications in complex carbohydrate synthesis. Representative structures of products formed by the preactivation-based dehydrative glycosylation of glycosyl hemiacetal. Retrosynthetic analysis of pentasaccharide

The chemistry and biology of mycolactones

• Matthias Gehringer and
• Karl-Heinz Altmann

Beilstein J. Org. Chem. 2017, 13, 1596–1660, doi:10.3762/bjoc.13.159

Total syntheses of the archazolids: an emerging class of novel anticancer drugs

• Stephan Scheeff and
• Dirk Menche

Beilstein J. Org. Chem. 2017, 13, 1085–1098, doi:10.3762/bjoc.13.108

• been described again by the Menche group following a sequence that was related to their archazolid A synthesis. Menche’s retrosynthetic analysis and strategy As a prelude to initiating a synthetic campaign directed towards the archazolids the Menche group first elucidated the full stereochemistry and

• synthesis was enabled by the group of Trauner and will be discussed below. Trauner’s retrosynthetic analysis and strategy Shortly after the total synthesis of archazolid A (1) by Menche et al. [41] the total synthesis of archazolid B 2 was reported by Trauner and co-workers [43]. As shown in Scheme 8, they

• to synthesize archazolid B (2) in only 19 steps from (S)-Roche ester 41 (longest linear sequence). O'Neil’s retrosynthetic analysis and strategy As discussed above one of the main difficulties of any archazolid synthesis involves the labile C1 to C5-dienoate system, which is prone to isomerization

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

• ’-transesterification is inevitable to occur in nucleosides [19][20][21]. The synthetic route would be lengthy and cumbersome. Therefore, a practical total synthesis is in high demand to facilitate the preparation of other kipukasins and their analogues. The retrosynthetic analysis is shown in Figure 2 (path b

• ) complexes with high yield and selectivity. The conditions are very mild and neutral. In the present paper, we continue to use ortho-alkynylbenzoate as protecting group for the 5’-OH group to fulfill the total synthesis of kipukasin A. According to the retrosynthetic analysis, we firstly started to synthesis

• -5''), 103.4 (C-5), 96.4 (C-3''), 87.4 (C-1'), 84.0 (C-4'), 73.2 (C-2'), 72.1 (C-3'), 62.2 (C-5'), 56.0 (OMe-4''), 55.5 (OMe-2''), 20.7 (Me-6'), 20.3 (Me-6''); HRMS (ESI) m/z: [M + Na]+ calcd for C21H24N2O10Na, 487.1329; found, 487.1327. Structures of kipukasins A–J. Retrosynthetic analysis of

Synthesis of D-manno-heptulose via a cascade aldol/hemiketalization reaction

• Yan Chen,
• Xiaoman Wang,
• Junchang Wang and
• You Yang

Beilstein J. Org. Chem. 2017, 13, 795–799, doi:10.3762/bjoc.13.79

• reported differentially protected ketoheptose building blocks may find further application in the preparation of structurally diverse D-manno-heptulose derivatives. Retrosynthetic analysis of D-manno-heptulose. Initial attempt on the synthesis of the C4 aldehyde from D-lyxose (5). Synthesis of

Total synthesis of a Streptococcus pneumoniae serotype 12F CPS repeating unit hexasaccharide

• Peter H. Seeberger,
• Claney L. Pereira and
• Subramanian Govindan

Beilstein J. Org. Chem. 2017, 13, 164–173, doi:10.3762/bjoc.13.19

• disaccharide branch at C3 of β-D-ManpNAcA and C3 of α-L-FucpNAc [15]. We established a total synthesis of the hexasaccharide repeat unit as a first step toward a detailed immunological analysis of S. pneumoniae 12F. Results and Discussion Retrosynthetic analysis. Initially, a convergent [3 + 3] synthesis of

Synthesis of acylhydrazino-peptomers, a new class of peptidomimetics, by consecutive Ugi and hydrazino-Ugi reactions

• Angélica de Fátima S. Barreto,
• Veronica Alves dos Santos and
• Carlos Kleber Z. Andrade

Beilstein J. Org. Chem. 2016, 12, 2865–2872, doi:10.3762/bjoc.12.285

• ) azapeptoid, (f) hydrazinopeptide and (g) hydrazinopeptoid. Some biologically active peptoids. Biologically active hydrazinopeptides and representation of the hydrazino turn. General structure of the acylhydrazino-peptomers synthesized in this study. Retrosynthetic analysis. Synthesis of hydrazides 3a–c

cis-Diastereoselective synthesis of chroman-fused tetralins as B-ring-modified analogues of brazilin

• Dimpee Gogoi,
• Runjun Devi,
• Pallab Pahari,
• Bipul Sarma and
• Sajal Kumar Das

Beilstein J. Org. Chem. 2016, 12, 2816–2822, doi:10.3762/bjoc.12.280

• . Retrosynthetic analysis of the designed B-ring-modified analogues of brazilin. The synthetic challenge associated with the synthesis of 5 by IFCEA of 6 (above) and recent literature reports of cis-diastereoselective synthesis of related tetracyclic molecules via intramolecular Friedel–Crafts cyclization

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

• applied to the synthesis of malasseziazoles by Knölker et al. [14]. However, the main challenge in retrosynthetic analysis was to achieve the regioselective cyclizaion, since the formation of undesired regioisomeric monocyclized products would block the further cyclization. If the reaction follows the

• materials. The operational simplicity combined with the convenience for introducing substituents to the aromatic rings makes this method useful. Natural indolo[3,2-a]carbazole alkaloids. Retrosynthetic analysis of indolo[3,2-a]carbazoles. Reagents and conditions: (a) H2SO4, MeOH; (b) Ar-NH2, Pd(OAc)2, BINAP

A new paradigm for designing ring construction strategies for green organic synthesis: implications for the discovery of multicomponent reactions to build molecules containing a single ring

• John Andraos

Beilstein J. Org. Chem. 2016, 12, 2420–2442, doi:10.3762/bjoc.12.236

• economy; green organic synthesis; integer partitioning; reactions; probability; retrosynthetic analysis; ring construction strategy; Introduction The ring motif is a key feature in chemical structures that has long attracted the attention of synthetic organic chemists in their quest to implement novel

• greenness. In research practice, synthetic organic chemists rely on a combination of retrosynthetic analysis [91][92][93][94][95][96][97], similarity and analogy patterning to known reactions, bond dissociation energy and bond polarity analysis (forward and umpolung), chemical intuition, and random

• vast library of reactions that they are familiar with from personal experience or through their readings of the literature. Extending known reaction strategy and bond forming-bond breaking themes by analogy is a very useful method. Though retrosynthetic analysis is a powerful tool in the arsenal, its

Enduracididine, a rare amino acid component of peptide antibiotics: Natural products and synthesis

• Darcy J. Atkinson,
• Briar J. Naysmith,
• Daniel P. Furkert and
• Margaret A. Brimble

Beilstein J. Org. Chem. 2016, 12, 2325–2342, doi:10.3762/bjoc.12.226

• . Synthesis of (±)-enduracididine (1) and (±)-allo-enduracididine (3). Synthesis of L-allo-enduracididine (3). Synthesis of protected L-allo-enduracididine 63. Synthesis of β-hydroxyenduracididine derivative 69. Synthesis of minosaminomycin (9). Retrosynthetic analysis of mannopeptimycin aglycone (77

Elongated and substituted triazine-based tricarboxylic acid linkers for MOFs

• Arne Klinkebiel,
• Ole Beyer,
• Barbara Malawko and
• Ulrich Lüning

Beilstein J. Org. Chem. 2016, 12, 2267–2273, doi:10.3762/bjoc.12.219

• the Suzuki–Miyaura coupling [11]. A retrosynthetic analysis (Figure 3) of extended mono-functionalized triazinetricarboxylic acids 2 calls for tris(4-bromoaryl)-1,3,5-triazines 3 and boronic acids 4 with an additional carboxylic acid functionality. The respective methyl carboxylate of boronic acid 4

• , right). The two structures in the lower half have been calculated with B3LYP//6-31G*. Mono-substituted TATB linkers 1b–d were successfully employed in the isoreticular syntheses of PCN-6 MOFs [10]. Retrosynthetic analysis for extended TATBs 2: triple Suzuki coupling between tribromotriazines 3 and

Practical synthetic strategies towards lipophilic 6-iodotetrahydroquinolines and -dihydroquinolines

• David R. Chisholm,
• Garr-Layy Zhou,
• Ehmke Pohl,
• Roy Valentine and
• Andrew Whiting

Beilstein J. Org. Chem. 2016, 12, 1851–1862, doi:10.3762/bjoc.12.174

• bromides or aryl chlorides, but initial investigation with 6-bromo-THQs indicated that these were remarkably unreactive in cross-coupling reactions [14], and a reliable and scalable synthesis of the likely more reactive iodides was, therefore, sought. We first considered the retrosynthetic analysis shown

Synthesis of the C8’-epimeric thymine pyranosyl amino acid core of amipurimycin

• Pramod R. Markad,
• Navanath Kumbhar and
• Dilip D. Dhavale

Beilstein J. Org. Chem. 2016, 12, 1765–1771, doi:10.3762/bjoc.12.165

• hydroxy and 1,2-dihydroxyethyl side chain at C3’ having a C8’ epimeric center, (b) an C5’ amino acid pendant and (c) the thymine nucleobase (2). Our results in this regard are described herein. Result and Discussion As shown in retrosynthetic analysis (Scheme 1), we envisioned that the substituted 2,7

Organic chemistry meets polymers, nanoscience, therapeutics and diagnostics

• Vincent M. Rotello

Beilstein J. Org. Chem. 2016, 12, 1638–1646, doi:10.3762/bjoc.12.161

• both art and photography at Illinois Institute of Technology, but science and scientists ended up deciding me. It started with Chem. 237, Organic Chemistry. This course was taught by Pete Johnson, who introduced me to retrosynthetic analysis, and in the process showed me how I could achieve the

NeoPHOX – a structurally tunable ligand system for asymmetric catalysis

• Jaroslav Padevět,
• Marcus G. Schrems,
• Robin Scheil and
• Andreas Pfaltz

Beilstein J. Org. Chem. 2016, 12, 1185–1195, doi:10.3762/bjoc.12.114

• phospinooxazoline ligands. Asymmetric hydrogenation with iridium-NeoPHOX catalysts [19]. Employing L-valine as a starting material for C5 substituted oxazoline. Retrosynthetic analysis for NeoPHOX ligands derived from serine and threonine. Crystal structures of selected Ir-complexes. Hydrogen atoms, COD and BArF

• anions were omitted for clarity. Retrosynthetic analysis for NeoPHOX ligands. Synthesis of 1st generation NeoPHOX Ir-complexes [19]. Synthesis of a C(5)-disubstituted NeoPHOX-Ir complex. Revisited synthetic strategy for the preparation of a threonine-based NeoPHOX ligand. Undesired β-lactam formation

Towards the total synthesis of keramaphidin B

• Pavol Jakubec,
• Alistair J. M. Farley and
• Darren J. Dixon

Beilstein J. Org. Chem. 2016, 12, 1096–1100, doi:10.3762/bjoc.12.104

• reported in due course. Keramaphidin B (1). Retrosynthetic analysis of keramaphidin B. Enantio- and diastereoselective bifunctional thiourea 12 organocatalysed Michael addition. (a) CO(OMe)2, LHMDS, THF, −78 °C to rt, 83%; (b) 20 mol % 12, toluene, −20 °C, 24 h, 95:5 dr (13:14), 90:10 er for 13, 99% yield

Catalytic asymmetric formal synthesis of beraprost

• Yusuke Kobayashi,
• Ryuta Kuramoto and
• Yoshiji Takemoto

Beilstein J. Org. Chem. 2015, 11, 2654–2660, doi:10.3762/bjoc.11.285

• Our retrosynthetic analysis for 2 is shown in Scheme 1, with the derivatization of 2 to beraprost (1) having already been reported. We planned to introduce the ester side chain on the aromatic ring at a later stage, utilizing radical-mediated reactions with acrylate [22] when the functional group (X

• (1). Retrosynthetic analysis of beraprost (1). Preparation of Michael precursors 7 and 8. First attempt at the synthesis of 2 from 6. Achievement of a formal synthesis of 2. Optimization of asymmetric intramolecular oxa-Michael reaction. Supporting Information Supporting Information File 476

Total synthesis of panicein A₂

• Lili Yeung,
• Lisa I. Pilkington,
• Melissa M. Cadelis,
• Brent R. Copp and
• David Barker

Beilstein J. Org. Chem. 2015, 11, 1991–1996, doi:10.3762/bjoc.11.215

• with the earlier report that stated 5 exhibits in vitro cytotoxicity against a number of cell lines (ED50 = 5 μg/mL). Members of the panicein family of aromatic sesquiterpenoids. Proposed biogenesis of panicein A2 (5). Retrosynthetic analysis of panicein A2 (5). Synthesis of ketone 13. Synthesis of

Design and synthesis of propellane derivatives and oxa-bowls via ring-rearrangement metathesis as a key step

• Sambasivarao Kotha and
• Rama Gunta

Beilstein J. Org. Chem. 2015, 11, 1727–1731, doi:10.3762/bjoc.11.188

• target molecule, eventually to arrive at simple starting materials by working in an opposite direction to a chemical synthesis. The ‘retrosynthetic analysis’ was first introduced by E. J. Corey and defined as “it is a problem solving technique for transforming the structure of a synthetic target molecule

• to a sequence of progressively simpler structures along a pathway which ultimately leads to a simple or commercially available starting materials for a chemical synthesis” [1] . Generally, this type of retrosynthetic analysis has been used to design [2][3][4][5][6] the target molecule. However, a

Synthesis of a tricyclic lactam via Beckmann rearrangement and ring-rearrangement metathesis as key steps

• Sambasivarao Kotha,
• Ongolu Ravikumar and
• Jadab Majhi

Beilstein J. Org. Chem. 2015, 11, 1503–1508, doi:10.3762/bjoc.11.163

• ; found, 224.1041. Retrosynthetic analysis of tricyclic amide 1. Molecular crystal structure of compound 11b. Synthesis of tricyclic ketone 4. Beckmann rearrangement of oximes 8a and 8b. Beckmann rearrangement reaction in a single step. Synthesis of ring-rearrangement precursors. Synthesis of Beckmann

Spiro annulation of cage polycycles via Grignard reaction and ring-closing metathesis as key steps

• Sambasivarao Kotha,
• Mohammad Saifuddin,
• Rashid Ali and
• Gaddamedi Sreevani

Beilstein J. Org. Chem. 2015, 11, 1367–1372, doi:10.3762/bjoc.11.147

• -closing metathesis (RCM) are considered as viable options. The retrosynthetic analysis to the target bis-spiro-cage compound 7 is shown in Figure 2. The target compound 7 could be obtained from O-allylation of the Grignard addition product 11 followed by the two-fold RCM sequence. The required cage dione

• synthesis of interesting cage molecules are in progress. Structures of diverse biologically as well as theoretically interesting molecules. Retrosynthetic analysis of bis-spiro-pyrano cage compound 7. (a)Optimized structure of 12, (b) optimized structure of 13. (a) Optimized structure of 18, (b) optimized

An intramolecular C–N cross-coupling of β-enaminones: a simple and efficient way to precursors of some alkaloids of Galipea officinalis

• Hana Doušová,
• Radim Horák,
• Zdeňka Růžičková and
• Petr Šimůnek

Beilstein J. Org. Chem. 2015, 11, 884–892, doi:10.3762/bjoc.11.99

• 1a. For selected parameters see Supporting Information File 1. Enaminone-based synthesis of (S)-cuspareine. The approaches to 2-aroylmethylidene-1,2,3,4-tetrahydroquinolines 1. The retrosynthetic analysis of the starting substrates for C–N cross-coupling. The synthesis of methyl 3-phenylpropionates

NAA-modified DNA oligonucleotides with zwitterionic backbones: stereoselective synthesis of A–T phosphoramidite building blocks

• Boris Schmidtgall,
• Claudia Höbartner and
• Christian Ducho

Beilstein J. Org. Chem. 2015, 11, 50–60, doi:10.3762/bjoc.11.8

• employed 'dimeric' T–T phosphoramidites 6 [38] for the automated synthesis of NAA-modified oligonucleotides; new 'dimeric' A–T phosphoramidites 7 as target structures of this study (DMTr = 4,4'-dimethoxytrityl). Retrosynthetic analysis of target phosphoramidites (S)-7 and (R)-7 (BOM = benzyloxymethyl

A carbohydrate approach for the formal total synthesis of (−)-aspergillide C

• Pabbaraja Srihari,
• Namballa Hari Krishna,
• Ydhyam Sridhar and
• Ahmed Kamal

Beilstein J. Org. Chem. 2014, 10, 3122–3126, doi:10.3762/bjoc.10.329

• approach has been a conventional strategy to achieve the total synthesis of complex, natural products with known handedness. Herein we disclose our strategy for the formal total synthesis of (−)-aspergillide C in a concise manner following the chiron approach. Retrosynthetic Analysis Through a

• retrosynthetic analysis, we envisaged that the macrolide 3 could be prepared from the seco acid 4 which can be easily accessed from 5 in five steps (Scheme 1). Compound 5, in turn, can be synthesized from commercially available tri-O-acetyl-D-galactal (6) and alkyne 7 through a Ferrier-type C-glycosylation

• tri-O-acetyl-D-galactal. A C-glycosidation, Trost’s hydrosilylation and protodesilylation protocol have been used as the key steps for achieving the formal total synthesis. Structures of aspergillides. Key NOESY correlations observed in compound 11. Retrosynthetic analysis for (−)-aspergillide C