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