Convergent synthesis of the tetrasaccharide repeating unit of the cell wall lipopolysaccharide of Escherichia coli O40

• Abhijit Sau and
• Anup Kumar Misra

Beilstein J. Org. Chem. 2012, 8, 2053–2059, doi:10.3762/bjoc.8.230

• compound 7 was confirmed from its spectral analysis [signals at δ 4.73 (d, J = 8.0 Hz, H-1B), 4.41 (br s, H-1A) in the 1H NMR and at δ 101.6 (C-1A), 100.7 (C-1B) in the 13C NMR spectra respectively]. Saponification of compound 7 by using sodium methoxide followed by 3,4-O-isopropylidenation with 2,2

Automated synthesis of sialylated oligosaccharides

• Davide Esposito,
• Mattan Hurevich,
• Bastien Castagner,
• Cheng-Chung Wang and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2012, 8, 1601–1609, doi:10.3762/bjoc.8.183

• with a benzoyl group at the C3 hydroxy position resulted in a lower glycosylation yield (36%), suggesting that an ester can lower the nucleophilicity of the vicinal C4-hydroxy. The synthesis was completed by deacetylation of compound 15 under Zemplén's conditions, followed by saponification and

• were applied to the synthesis of GM3 trisaccharide 16 previously prepared in solution phase (see above). Glucose thioglycoside building block 21 and disaccharide building block 4 served for the assembly of 16 (Scheme 4). Final saponification afforded the partially protected glycan 22 in 40% overall

• optimized conditions, the branched tetrasaccharide 26 was isolated in 51% overall yield after TCA reduction, cleavage, ester saponification and HPLC purification. Finally, solution-phase hydrogenolysis gave tetrasaccharide 27. Automated synthesis of linear α–(2→6) sialosides α-(2→6) Sialylated

Stereoselective synthesis of trans-fused iridoid lactones and their identification in the parasitoid wasp Alloxysta victrix, Part II: Iridomyrmecins

• Robert Hilgraf,
• Nicole Zimmermann,
• Lutz Lehmann,
• Armin Tröger and
• Wittko Francke

Beilstein J. Org. Chem. 2012, 8, 1256–1264, doi:10.3762/bjoc.8.141

• C and D was completed in three additional steps (Scheme 2). The oxidation with Jones reagent yielded 14, and subsequent saponification of the acetate group with methanolic KOH afforded the hydroxy acid 6. Similar to the approach described above, careful lactonization with DCC and DMAP gave

Stereoselective synthesis of trans-fused iridoid lactones and their identification in the parasitoid wasp Alloxysta victrix, Part I: Dihydronepetalactones

• Nicole Zimmermann,
• Robert Hilgraf,
• Lutz Lehmann,
• Daniel Ibarra and
• Wittko Francke

Beilstein J. Org. Chem. 2012, 8, 1246–1255, doi:10.3762/bjoc.8.140

• furnish the primary alcohol 31, which upon oxidation will yield the corresponding aldehyde that can be epimerized to the diastereomers 32/32* as shown above. Subsequent reduction of 32/32*, silylation of the resulting primary alcohols and saponification will produce a mixture of the diastereoisomers 33/33

Partial thioamide scan on the lipopeptaibiotic trichogin GA IV. Effects on folding and bioactivity

• Marta De Zotti,
• Barbara Biondi,
• Cristina Peggion,
• Matteo De Poli,
• Haleh Fathi,
• Simona Oancea,
• Claudio Toniolo and
• Fernando Formaggio

Beilstein J. Org. Chem. 2012, 8, 1161–1171, doi:10.3762/bjoc.8.129

• : Deprotection by catalytic hydrogenation with Pd/C. 4: Thionation with Lawesson's reagent in THF. 5: Coupling with n-Oct-OH in the presence of EDC/HOBt. 6: Saponification with NaOH/MeOH. 7: Coupling in the presence of EDC/HOAt. Synthesis of ψ[CS-NH]5. 1: Coupling in the presence of EDC/HOBt. 2: Deprotection by

Two-directional synthesis as a tool for diversity-oriented synthesis: Synthesis of alkaloid scaffolds

• Kieron M. G. O’Connell,
• Monica Díaz-Gavilán,
• Warren R. J. D. Galloway and
• David R. Spring

Beilstein J. Org. Chem. 2012, 8, 850–860, doi:10.3762/bjoc.8.95

• EtOH and H2O under reflux to achieve ester saponification, which was followed by decarboxylation, proceeding smoothly to give the corresponding ketone in 76% yield. The ketone was then transformed to the exocyclic alkene 15 in 61% yield by Wittig reaction with the appropriate phosphonium salt. The

Synthesis and antifungal properties of papulacandin derivatives

• Marjolein van der Kaaden,
• Eefjan Breukink and
• Roland J. Pieters

Beilstein J. Org. Chem. 2012, 8, 732–737, doi:10.3762/bjoc.8.82

• synthesis started with the saponification of 15, followed by the protection of O-4 and O-6 by using di-tert-butylsilyl bis(trifluoromethanesulfonate). Subsequent protection of O-3 with TES-Cl, gave the fully protected glucal 18. According to Denmark et al. [31], lithiation and silylation of 18 should give

Synthesis of fluorinated maltose derivatives for monitoring protein interaction by ¹⁹F NMR

• Michaela Braitsch,
• Hanspeter Kählig,
• Georg Kontaxis,
• Michael Fischer,
• Toshinari Kawada,
• Robert Konrat and
• Walther Schmid

Beilstein J. Org. Chem. 2012, 8, 448–455, doi:10.3762/bjoc.8.51

• anomeric acetyl group of compound 2 with hydrazine acetate [29] yielding derivative 7, followed by nucleophilic fluorination with DAST [30][31] generating the diasteriomeric mixture 8. The α-anomer was isolated by HPLC and subsequent Zemplén saponification of the remaining acetate protecting groups yielded

• with Pd/C [36], followed by a Zemplén saponification to obtain product 15. Starting from 4′,6′-O-benzylidene maltose 10 [37], the primary alcohol was protected as tert-butyldimethylsilyl ether followed by standard peracetylation (Scheme 2). Treatment of the silyl protecting group with an excess of

Complete transfer of chirality in an intramolecular, thermal [2 + 2] cycloaddition of allene-ynes to form non-racemic spirooxindoles

• Kay M. Brummond and
• Joshua M. Osbourn

Beilstein J. Org. Chem. 2011, 7, 601–605, doi:10.3762/bjoc.7.70

• commenced with the preparation of the enantiopure propargyl acetate 7 [8]. Treatment of racemic propargyl alcohol 4 with the (R)-acid chloride 5, DMAP, and pyridine resulted in propargyl ester 6 as a separable 4:1 mixture of diastereomers. Saponification of the major diastereomer of 6, followed by acylation

An overview of the key routes to the best selling 5-membered ring heterocyclic pharmaceuticals

• Marcus Baumann,
• Ian R. Baxendale,
• Steven V. Ley and
• Nikzad Nikbin

Beilstein J. Org. Chem. 2011, 7, 442–495, doi:10.3762/bjoc.7.57

• ethyl 3-oxopropanoate followed by saponification of the ester to yield etodolac (Scheme 31) [44]. The second described route [45][46] is similar but starts with a more readily available carbonyl surrogate; 2,3-dihydrofuran 154. The Fischer indole reaction provides a primary alcohol which is TMS

• -protected and condensed with methyl 3-oxopentanoate under Lewis acid conditions. The use of the temporary silyl mask was found beneficial as it circumvents the need for chromatographic purification. Finally, simple saponification furnishes etodolac (Scheme 32). Extensive biological studies have found that

Oxidative allylic rearrangement of cycloalkenols: Formal total synthesis of enantiomerically pure trisporic acid B

• Silke Dubberke,
• Muhammad Abbas and
• Bernhard Westermann

Beilstein J. Org. Chem. 2011, 7, 421–425, doi:10.3762/bjoc.7.54

• synthesis of this stereogenic unit and solutions have been found, e.g., by Christoffers and d’Angelo [9][10][11]. We have already disclosed our results to obtain these products highly enantiomerically enriched by pig liver esterase (PLE) catalyzed saponification of α-substituted β-ketoesters [12][13]. We

• have now extended this methodology towards the saponification of unsaturated β-ketoesters (±)-1a,b (Scheme 1) to provide a convenient access to highly functionalized cyclohexenones in optically pure form. In addition, we show that non-racemic chiral α-substituted, β-ketoesters such as (−)-1c can be

• -ketoester 1c, the racemate 1c is resolved by a pig liver esterase (PLE)-catalyzed saponification reaction. As in other cases reported earlier, the racemic β-ketoesters are hydrolyzed with high stereoselectivity allowing the isolation of optically pure esters (–)-1. The corresponding hydrolysis products, the

A two step synthesis of a key unit B precursor of cryptophycins by asymmetric hydrogenation

• Benedikt Sammet,
• Mathilde Brax and
• Norbert Sewald

Beilstein J. Org. Chem. 2011, 7, 243–245, doi:10.3762/bjoc.7.32

• final saponification reaction to give carboxylic acid 5 (Scheme 1). A number of experimental procedures for this route have been published [5][6][7]. The selective monochlorination of D-tyrosine is quite cumbersome since the formation of the dichlorinated product must be minimized and the presence of

Application of the diastereoselective photodeconjugation of α,β-unsaturated esters to the synthesis of gymnastatin H

• Ludovic Raffier and
• Olivier Piva

Beilstein J. Org. Chem. 2011, 7, 151–155, doi:10.3762/bjoc.7.21

• ) configuration at the C-6 carbon. By saponification under mild conditions, 24 was converted into carboxylic acid 25 which was implicated into a free-epimerising amidation procedure with HOBt [22] and the readily available O-protected tyrosine derivative 26. Finally, the TBS group of the amino ester moiety was

Synthesis, electronic properties and self-assembly on Au{111} of thiolated (oligo)phenothiazines

• Adam W. Franz,
• Svetlana Stoycheva,
• Michael Himmelhaus and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2010, 6, No. 72, doi:10.3762/bjoc.6.72

• prepared from (oligo)phenothiazinyl thioacetates 2 or 4 by in situ saponification with degassed aqueous ammonia in THF at room temperature for 24 h (Scheme 2). Based upon thorough surface analysis of the previously studied thiolated phenylethynyl phenothiazines chemisorbed on Au{111} by ellipsometry

Efficient and improved synthesis of Telmisartan

• A. Sanjeev Kumar,
• Samir Ghosh and
• G. N. Mehta

Beilstein J. Org. Chem. 2010, 6, No. 25, doi:10.3762/bjoc.6.25

• the benzimidazole derivative 3. After saponification, the free carboxyl group is condensed with N-methyl-1,2-phenylenediamine to afford the bis-benzimidazole 4, which is then alkylated with the 4′-(bromomethyl)-2-biphenylcarboxylic acid tert-butyl ester (8) to give, after hydrolysis of the ester group

Enantioselective synthesis of tricyclic amino acid derivatives based on a rigid 4-azatricyclo[5.2.1.0^2,6]decane skeleton

• Matthias Breuning,
• Tobias Häuser,
• Christian Mehler,
• Christian Däschlein,
• Carsten Strohmann,
• Andreas Oechsner and
• Holger Braunschweig

Beilstein J. Org. Chem. 2009, 5, No. 81, doi:10.3762/bjoc.5.81

• , after saponification, the endo-configured acid 21 as a single diastereomer. The further conversion of 21 into the target molecules was carried out in analogy to the preparation of 7a/b•HCl from 19 (see Scheme 4), giving 8a•HCl in overall 24% yield from 9 (four steps) and 8b•HCl in overall 10% yield

Ring strain and total syntheses of modified macrocycles of the isoplagiochin type

• Andreas Speicher,
• Timo Backes,
• Kerstin Hesidens and
• Jürgen Kolz

Beilstein J. Org. Chem. 2009, 5, No. 71, doi:10.3762/bjoc.5.71

• and 26 were prepared as the “d” ring for Suzuki coupling with the bromoarene 16 (Scheme 5). First, iodination of 3-hydroxybenzoic acid (18) followed by double methylation and saponification of the methyl ester yielded 4-iodo-3-methoxybenzoic acid (19) which could be reduced in two steps [27] to the

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

• macrocyclization. Hydrogenation of the olefins followed by saponification of macrolactones 106 and 107 with NaOMe and subsequent MOM protection gave the common intermediate 108 with identical physical data independent of the route used. The lithium enolate formed from 108 with LDA was treated with 109 and the

Diastereoselective and enantioselective reduction of tetralin- 1,4-dione

• E. Peter Kündig and
• Alvaro Enriquez-Garcia

Beilstein J. Org. Chem. 2008, 4, No. 37, doi:10.3762/bjoc.4.37

• % yield). Saponification and fractional recrystallization from MeOH / Et2O then afforded pure 6 and 7 though isolated yields were not reported [9]. The meso-diol 6 has been used as substrate in enantioselective oxidation [10] and in asymmetric acylation [9][11]. We conclude that while conditions for an

Sordarin, an antifungal agent with a unique mode of action

• Huan Liang

Beilstein J. Org. Chem. 2008, 4, No. 31, doi:10.3762/bjoc.4.31

• into 75 by protection of the OH group with TBDPSCl and saponification of the benzoate ester (LiOH). Lewis acid-induced glycosylation [46] of 75 with trichloroacetimidate 76 gave 77. The latter was then subjected to TBAF deprotection, PCC oxidation, and Pd/C hydrogenation, to afford analog 78. Isopentyl

• ether 80 was prepared via ethylene glycol protection, saponification, alkylation by prenyl bromide, hydrogenation and acetonide cleavage. Two other analogs were assembled from 70 by LiOH hydrolysis of the benzoate ester and Pd/C hydrogenolysis of the benzyl one. While biological tests indicated that

Stereoselective α-fluoroamide and α-fluoro- γ-lactone synthesis by an asymmetric zwitterionic aza-Claisen rearrangement

• Kenny Tenza,
• Julian S. Northen,
• David O'Hagan and
• Alexandra M. Z. Slawin

Beilstein J. Org. Chem. 2005, 1, No. 13, doi:10.1186/1860-5397-1-13

• -fluoropropionyl chloride 9 were explored but the method of choice involved nucleophilic fluorination of the mesylate 7 with KF to give ethyl 2-fluoropropionate 8 (Scheme 2).[19] Saponification and then treatment with phthaloyl dichloride gave 9 after distillation. 2-Fluorophenylacetyl chloride was prepared from