Synthesis of trifunctional cyclo-β-tripeptide templates

• Frank Stein,
• Tahir Mehmood,
• Tilman Plass,
• Javid H. Zaidi and
• Ulf Diederichsen

Beilstein J. Org. Chem. 2012, 8, 1576–1583, doi:10.3762/bjoc.8.180

• prepared from the respective β-amino acids by Arndt–Eistert homologation [17][18][19]. The β-amino acids were transformed into the respective diazoketones with isobutyl chloroformate, triethylamine and diazomethane. The ketones were further converted into the β-amino acids by Wolff rearrangement using

• solution of diazomethane (181 mL, 54.2 mmol, 2.00 equiv) in Et2O was added. After 15 min, the reaction mixture was stirred for an additional 6 h at room temperature. Excess diazomethane was decomposed by dropwise addition of AcOH. The solvent was removed under reduced pressure, and the residue was

Equilibrium constants and protonation site for N-methylbenzenesulfonamides

• José A. Moreira,
• Ana M. Rosa da Costa,
• Luis García-Río and
• Márcia Pessêgo

Beilstein J. Org. Chem. 2011, 7, 1732–1738, doi:10.3762/bjoc.7.203

• importance in the studies of the nitroso-group transfer mechanism from 1. Such compounds react with a variety of nucleophiles: In the presence of HO− or EtO−, which attack their SO2 group, decomposition to afford diazomethane occurs [1][2]. In acidic medium, they undergo denitrosation to the corresponding N

Effects of anion complexation on the photoreactivity of bisureido- and bisthioureido-substituted dibenzobarrelene derivatives

• Heiko Ihmels and
• Jia Luo

Beilstein J. Org. Chem. 2011, 7, 278–289, doi:10.3762/bjoc.7.37

• dibenzobarrelene derivative 1c which forms the chiral ammonium carboxylate 1c-P with (S)-proline (Scheme 2). After irradiation, acidic workup and subsequent esterification with diazomethane, the dibenzosemibullvalene 2c was obtained with high enantiomeric excess (>95% ee) [35][36]. Interestingly, several

Photoinduced homolytic C–H activation in N-(4-homoadamantyl)phthalimide

• Nikola Cindro,
• Margareta Horvat,
• Kata Mlinarić-Majerski,
• Axel G. Griesbeck and
• Nikola Basarić

Beilstein J. Org. Chem. 2011, 7, 270–277, doi:10.3762/bjoc.7.36

• diazomethane, generated in situ from N-methyl-N-nitroso-p-toluenesulfonamide (Diazald®) [56]. Homoadamantanone 3 was first reduced to the alcohol 4 [57][58][59] and subsequently converted to homoadamantyl phthalimide 5 in moderate yield via the Mitsunobu protocol [60] (Scheme 2). To get more insight into the

Synthesis of oxa-bridged derivatives from Diels–Alder bis-adducts of butadiene and 1,2,3,4-tetrahalo-5,5-dimethoxycyclopentadiene

• Faiz Ahmed Khan and
• Karuppasamy Parasuraman

Beilstein J. Org. Chem. 2010, 6, No. 64, doi:10.3762/bjoc.6.64

• reaction was carried out in presence of the phase transfer catalyst TBHSO4 the bis-oxa-bridged compounds 8 and 10 were obtained (after esterification with diazomethane) in 31 and 37%, respectively (Scheme 3). The relative stereochemistry in 8 was unambiguously established by the single crystal X-ray

• treated first with alkaline H2O2 and then with additional NaOH (60 equiv) at 60 °C followed by esterification with diazomethane to obtain the oxa-bridged compound 8 in 42% yield. Bis-diketone 15 was transformed into 10 in 39% yield by a similar method. Unlike the bis-diketones in chloro series (7 and 9

Synthesis of glycosylated β³-homo-threonine conjugates for mucin-like glycopeptide antigen analogues

• Florian Karch and
• Anja Hoffmann-Röder

Beilstein J. Org. Chem. 2010, 6, No. 47, doi:10.3762/bjoc.6.47

• by Norgren et al. [29]. TN antigen derivative Fmoc-Thr(αAc3GalNAc)-OH (1a) was prepared according to published procedures [32][33] and converted into the corresponding diazo ketone upon treatment with isobutyl chloroformate in the presence of N-methylmorpholine (NMM) and diazomethane (Scheme 1

• Micromass Q TOF Ultima 3 spectrometer and optical rotations were measured at 546 nm with a Perkin-Elmer polarimeter 241. General procedure for the synthesis of diazomethane in ethereal solution Caution: Diazomethane is toxic, highly-volatile, cancerogenic and explosive. Its generation and handling thus

• resulting suspension was stirred for 20 min at this temperature. The mixture was allowed to reach 0 °C and the diazomethane solution in Et2O was added. The yellow solution was stirred 20 min at 0 °C before it was allowed to reach room temperature and stirred for further 16 h. Excess of diazomethane was

Synthesis and binding studies of two new macrocyclic receptors for the stereoselective recognition of dipeptides

• Ana Maria Castilla,
• M. Morgan Conn and
• Pablo Ballester

Beilstein J. Org. Chem. 2010, 6, No. 5, doi:10.3762/bjoc.6.5

• ][27][28][29] to obtain the Fmoc N-protected amino acid that was subsequently esterified with diazomethane affording Fmoc-I-Phe-OMe, 4d. The diprotected aryl iodides, 4a and 4b, were converted uneventfully to the corresponding diprotected aryl trimethylstannane derivatives, 5a and 5b, by reaction with

Studies on polynuclear furoquinones. Part 1: Synthesis of tri- and tetra- cyclic furoquinones simulating BCD/ABCD ring system of furoquinone diterpenoids

• Faruk H. Shaik and
• Gandhi K. Kar

Beilstein J. Org. Chem. 2009, 5, No. 47, doi:10.3762/bjoc.5.47

• was thoroughly extracted with ethyl acetate. After usual work up, 80 mg (85%) of the acid 9 was obtained as white solid, m.p., 197–199 °C. IR (KBr) νmax 1692.2 cm−1. (Treatment of the acid 9 with diazomethane in ether produced the methyl ester derivative identical with compound 8.) Phenanthro[1,2-b

A simple route for renewable nano- sized arjunolic and asiatic acids and self- assembly of arjuna- bromolactone

• Braja G. Bag,
• Partha P. Dey,
• Shaishab K. Dinda,
• William S. Sheldrick and
• Iris M. Oppel

Beilstein J. Org. Chem. 2008, 4, No. 24, doi:10.3762/bjoc.4.24

• transformed to a mixture of arjuna-bromolactone 3 and unchanged asiatic acid (2) on reaction with bromine in acetic acid, using the reactivity differences of the triterpenic acids towards bromolactonization [9][15]. A suspension of the mixture of 2 and 3 in methanol with ethereal diazomethane yielded a