Synthesis of rigid p-terphenyl-linked carbohydrate mimetics

• Maja Kandziora and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2014, 10, 1749–1758, doi:10.3762/bjoc.10.182

• understanding of this unexpected result the reductive cleavage was examined with the simpler bicyclic 1,2-oxazine derivative 12a. Here the unexpected bicyclic compound 24 was isolated as major product in 79% yield together with the desired aminopyran derivative 25 in 14% yield. It was observed by 1H NMR

• methanol/THF. In summary, by optimizing the protective group strategy and the reductive cleavage methods we were able to prepare the desired rigid p-terphenyl-linked carbohydrate mimetic 30 in twelve steps starting from D-isoascorbic acid, but in only six steps with respect to crucial intermediate 4. The

• , rt, 24 h. Synthesis of N-benzylated p-terphenyl derivative 21 by Suzuki cross-coupling of 12a with 20 and subsequent reduction with zinc. Conditions: a) Pd(PPh3)4, 2 M Na2CO3 aq, THF/DMF (8:2), 70 °C, 48 h; b) Zn, AcOH, THF, 60 °C, 18 h. Attempted reductive cleavage of the N–O bond of compound 21 by

Allenylphosphine oxides as simple scaffolds for phosphinoylindoles and phosphinoylisocoumarins

• G. Gangadhararao,
• Ramesh Kotikalapudi,
• M. Nagarjuna Reddy and
• K. C. Kumara Swamy

Beilstein J. Org. Chem. 2014, 10, 996–1005, doi:10.3762/bjoc.10.99

• which the benzyl group also was cleaved (NMR evidence). Such a reductive cleavage of the P–C bond from phosphinoyl indoles is a reaction that we are still exploring. A plausible pathway for the formation of phosphinoylindoles 6 and 9–19 is shown in Scheme 6. As depicted above in Scheme 2, the normal

Preparation of new alkyne-modified ansamitocins by mutasynthesis

• Kirsten Harmrolfs,
• Lena Mancuso,
• Binia Drung,
• Florenz Sasse and
• Andreas Kirschning

Beilstein J. Org. Chem. 2014, 10, 535–543, doi:10.3762/bjoc.10.49

• ] were one of the earliest examples of folate disulfide–drug conjugates and after the conjugate is internalized by endocytosis, it was demonstrated that the endosomes exert reductive cleavage. For conjugate 7 we found that disulfide cleavage provided a thiol derivative of ansamitocin P-3 (4, AP-3) 8 with

• after reductive cleavage, ansamitocin derivative 8 still showed sufficient antiproliferative activity. This is in line with our observation that structural changes at the aromatic ring do not affect the biological properties of the ansamitocins to a great extent [13][14][15][16][17][18][19][20][21]. In

Synthesis of the B-seco limonoid core scaffold

• Hanna Bruss,
• Hannah Schuster,
• Rémi Martinez,
• Markus Kaiser,
• Andrey P. Antonchick and
• Herbert Waldmann

Beilstein J. Org. Chem. 2014, 10, 194–208, doi:10.3762/bjoc.10.15

• 19 and 20 were obtained. In order to synthesize a model substrate without the rigid BDA-protecting group, compound 21 was treated with aqueous TFA to give a triol which was masked with three MOM-protecting groups (Scheme 3). Reductive cleavage of the pivaloyl group furnished alcohol 22. Mesylation or

Synthesis, characterization and initial evaluation of 5-nitro-1-(trifluoromethyl)-3H-1λ³,2-benziodaoxol-3-one

• Nico Santschi,
• Roman C. Sarott,
• Elisabeth Otth,
• Reinhard Kissner and
• Antonio Togni

Beilstein J. Org. Chem. 2014, 10, 1–6, doi:10.3762/bjoc.10.1

• -substituted compounds. When comparing the same unit I–X within the analogous compounds 2 and 3, a shorter bond would intuitively correspond to a stronger bond. Therefore, based on simple geometrical parameters, reagent 3 was expected to be slightly less reactive compared to 2, meaning that reductive cleavage

An overview of the synthetic routes to the best selling drugs containing 6-membered heterocycles

• Marcus Baumann and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2013, 9, 2265–2319, doi:10.3762/bjoc.9.265

• is achieved via an asymmetric addition of phenylethylzinc to the imine N-oxide 2.66 yielding the corresponding 3,4-dihydroisoquinoline-N-hydroxide 2.68. Further reductive cleavage of the hydroxylamine moiety followed by activation with 4-nitrophenyl chloroformate [79] yields the intermediate 2.69. In

Polymeric redox-responsive delivery systems bearing ammonium salts cross-linked via disulfides

• Christian Dollendorf,
• Martin Hetzer and
• Helmut Ritter

Beilstein J. Org. Chem. 2013, 9, 1652–1662, doi:10.3762/bjoc.9.189

• successfully synthesized by cross-linking reactions via quaternary ammonium compounds with the disulfide-bearing cross-linker CL 1. The ability of the polymer network to enclose and release substances by reductive cleavage or oxidative formation of disulfide bonds was shown exemplarily using different dyes

• poly(DEAAm-co-DMAEMA) (right) in distilled water. (b) Reductive cleavage of cross-linked poly(DEAAm-co-DMAEMA) networks containing phenolphthalein in pH 10 buffer solution. Storage modulus G’ as function of applied shear stress τ for samples 4 and 5 containing different amounts of CL 1 or CL 2. Storage

• (empty symbols) and 30% H2O2 (half symbols). Swelling degree Q of polymer discs 4–6 as a function of the amount and type of containing cross-linker. (a) Synthesis of a polycationic cross-linked hydrogel containing disulfide groups. (b) Reductive cleavage and oxidative rebuilding of disulfide groups in

Novel synthesis of pseudopeptides bearing a difluoromethyl group by Ugi reaction and desulfanylation

• Jingjing Wu,
• Hui Li and
• Song Cao

Beilstein J. Org. Chem. 2011, 7, 1070–1074, doi:10.3762/bjoc.7.123

• continuation of our interest in the synthesis of diverse difluoromethyl-containing pseudopeptides, we herein report a novel and efficient synthesis of difluoromethyl-containing pseudopeptides through Ugi reaction, with gem-difluoromethylene-containing acid as a key component, followed by reductive cleavage of

• building block 2 were subjected to Ugi reaction under solvent-free conditions, followed by reductive cleavage of the phenylsulfanyl group. It was found that both Ugi reaction and desulfanylation proceeded smoothly for all substrates used to give the corresponding difluoromethylene-containing and

• building block 2,2-difluoro-2-(phenylthio)acetic acid (2) as one component, followed by removal of the phenylsulfanyl protecting group in the presence of tributyltin hydride and azobisisobutyronitrile. Keywords: difluoromethyl functionality; gem-difluoromethylene-containing acid; pseudopeptides; reductive

Photocycloaddition of aromatic and aliphatic aldehydes to isoxazoles: Cycloaddition reactivity and stability studies

• Axel G. Griesbeck,
• Marco Franke,
• Jörg Neudörfl and
• Hidehiro Kotaka

Beilstein J. Org. Chem. 2011, 7, 127–134, doi:10.3762/bjoc.7.18

• . Photochemical ring contraction of isoxazoles 7f–7h. Photocycloaddition of aromatic aldehydes to di- and trimethyl isoxazoles 7d and 7e. Preparative photocycloadditions of 7e with aromatic aldehydes. T-type photochromism of isoxazole–aldehyde pairs. Reductive cleavage of the trimethylisoxazole adduct 9a

Design and synthesis of a cyclitol-derived scaffold with axial pyridyl appendages and its encapsulation of the silver(I) cation

• Pierre-Marc Léo,
• Christophe Morin and
• Christian Philouze

Beilstein J. Org. Chem. 2010, 6, 1022–1024, doi:10.3762/bjoc.6.115

• , upon complexation with participation of three oxygen atoms in the binding, no substantial rearrangement of this semi-rigid structure is to be expected. In addition, reductive cleavage of one of the ortho-ester C–H benzylic bonds, which is known to yield a free hydroxy group [15][16], would allow