Synthesis and self-assembly of 1-deoxyglucose derivatives as low molecular weight organogelators

• Guijun Wang,
• Hao Yang,
• Sherwin Cheuk and
• Sherman Coleman

Beilstein J. Org. Chem. 2011, 7, 234–242, doi:10.3762/bjoc.7.31

• series of methyl 4,6-O-benzylidene-α-D-glucopyranoside (1) derivatives (Figure 1), including esters and carbamates with different functional groups. Several of these compounds proved to be effective gelators for organic solvents and aqueous solutions [34][35][36][37]. We found that the structures of the

Palladium- and copper-mediated N-aryl bond formation reactions for the synthesis of biological active compounds

• Carolin Fischer and
• Burkhard Koenig

Beilstein J. Org. Chem. 2011, 7, 59–74, doi:10.3762/bjoc.7.10

• , carbamates, N-heterocycles, enamines and intramolecular N-arylation reactions [45]. We compare here the success of the different C–N-arylation reactions as applied to the synthesis of more complex structures and discuss selected examples of palladium- and copper-mediated reactions for the synthesis of

Recent advances in carbocupration of α-heterosubstituted alkynes

• Ahmad Basheer and
• Ilan Marek

Beilstein J. Org. Chem. 2010, 6, No. 77, doi:10.3762/bjoc.6.77

• combined with its strong ability to coordinate organometallic derivatives have a major directing effect and favor formation of the α-isomer (Scheme 7) [19]. Thus, when alkynyl carbamates 12a,b are added to organocopper derivatives RCu•MgBr2 in Et2O at −78 °C for only 90 min, the expected linear products 13

• stereospecifically the trisubstituted enol carbamates as single isomers. It is important to note that the nature of solvent plays a critical role in the regioselectivity of this reaction. Diethyl ether leads to the linear product, whereas THF gives the branched product as the major reaction product (branched/linear

• N-substituted alkynes give the β-isomer due to the mesomeric effect of the heteroatom, except when an extra chelating moiety is present such as in alkynyl-O-carbamates, THPoxy-alkynes, and ynamides. In these cases, the opposite α-isomers are formed. P-, S- and Si-substituted alkynes all give the α

(Pseudo)amide-linked oligosaccharide mimetics: molecular recognition and supramolecular properties

• José L. Jiménez Blanco,
• Fernando Ortega-Caballero,
• Carmen Ortiz Mellet and
• José M. García Fernández

Beilstein J. Org. Chem. 2010, 6, No. 20, doi:10.3762/bjoc.6.20

• activities, probably due to the presence of a hydrophilic sugar substituent at the nitrogen atom of the nor-tropane ring [71][72]. Several groups have shown that disaccharide ureas and carbamates with different bridging positions as α/β-anomers are readily accessible by the coupling reaction of aminosugars

2-Phenyl- tetrahydropyrimidine- 4(1H)-ones – cyclic benzaldehyde aminals as precursors for functionalised β²-amino acids

• Markus Nahrwold,
• Arvydas Stončius,
• Anna Penner,
• Beate Neumann,
• Hans-Georg Stammler and
• Norbert Sewald

Beilstein J. Org. Chem. 2009, 5, No. 43, doi:10.3762/bjoc.5.43

• containing e.g. tert-butyl protected side chain functions. Amino acids protected like that are particularly suitable for solid phase peptide synthesis and are thus highly desirable. Our novel ring cleavage concept includes the protection of both ring-nitrogen atoms as carbamates (Scheme 1C). Similar to the

Convenient method for preparing benzyl ethers and esters using 2-benzyloxypyridine

• Susana S. Lopez and
• Gregory B. Dudley

Beilstein J. Org. Chem. 2008, 4, No. 44, doi:10.3762/bjoc.4.44

• (entry 7, 84%) and methyl lactate (3e, 79%) verify compatibility with esters and carbamates. Note that the benzylation of N-Boc-serine methyl ester (3d) compares favourably to analogous reactions reported previously [24], because the neutral reaction conditions described herein are compatible with the

Vinylogous Mukaiyama aldol reactions with 4-oxy-2-trimethylsilyloxypyrroles: relevance to castanospermine synthesis

• Roger Hunter,
• Sophie C. M. Rees-Jones and
• Hong Su

Beilstein J. Org. Chem. 2007, 3, No. 38, doi:10.1186/1860-5397-3-38

• doubt. Attention was then turned to changing the N-protecting group to a carbamate in line with TBSOP 1. The pyrroline precursor 4 (R1 = H, R2 = OMe) was readily prepared via condensation of ethyl E-4-chloro-3-methoxybut-2-enoate with ammonia, and then transformed to carbamates 4c and 4d under the

• pyrrolinone with formation of a multitude of products. This was attributed to the instability of the pyrrolinone carbamates 4c and 4d towards n-BuLi, and indicated the need to resort to the Casiraghi conditions of 2,6-lutidine and TBSOTf for silyloxypyrrole generation.[12] However, in view of our objective of

An asymmetric synthesis of all stereoisomers of piclavines A1-4 using an iterative asymmetric dihydroxylation

• Yukako Saito,
• Naoki Okamoto and
• Hiroki Takahata

Beilstein J. Org. Chem. 2007, 3, No. 37, doi:10.1186/1860-5397-3-37

• clean deprotection of Cbz. However, treatment of (2R-[4S])-16 with iodotrimethylsilane (TMSI)[13] in CH3CN provided the amine (75%), which was treated with TrocCl/K2CO3 to afford the Troc carbamates (2R-[4S])-17. After mesylation of [2S-(4R)]-17, N-deprotection of the resulting mesylate with 10% Cd-Pb

The oxanorbornene approach to 3-hydroxy, 3,4-dihydroxy and 3,4,5-trihydroxy derivatives of 2-aminocyclohexanecarboxylic acid

• Ishmael B. Masesane,
• Andrei S. Batsanov,
• Judith A. K. Howard,
• Raju Mondal and
• Patrick G. Steel

Beilstein J. Org. Chem. 2006, 2, No. 9, doi:10.1186/1860-5397-2-9

• carbamates we then sort to exploit the alkene units to provide a convenient source of poly-hydroxylated cyclohexane β-aminoacids. Consequently, treatment of endo derived hydroxy diene with mCPBA in DCM afforded a separable 9:1 mixture of epoxides 10 and 11 favouring addition syn to the carbamate, Scheme 3

• reaction. Concurring with our results, Donohoe has reported that cyclic homoallylic carbamates give high levels of syn selectivity in the OsO4 mediated dihydroxylation reactions.[25][26] On the other hand, Kishi has established that the OsO4 mediated oxidation of cyclic allylic alcohols led preferentially

Total syntheses of oxygenated brazanquinones via regioselective homologous anionic Fries rearrangement of benzylic O-carbamates

• Glaucia Barbosa Candido Alves Slana,
• Mariângela Soares de Azevedo,
• Rosângela Sabattini Capella Lopes,
• Cláudio Cerqueira Lopes and
• Jari Nobrega Cardoso

Beilstein J. Org. Chem. 2006, 2, No. 1, doi:10.1186/1860-5397-2-1

• new variations of anionic aromatic chemistry, the total synthesis of oxygenated brazanquinones (1a-1c), derived from β-brasan, a natural product isolated from Caesalpina echinata, via carbamates 2a-2c is described. Introduction The search for new synthetic routes for the total synthesis of

• -diethylcarbamoyl chloride, and sodium hydride afforded the carbamates 2a-2d (Scheme 2). The carbamates 2a-2c were cyclized in the presence of excess sec-BuLi in THF at -78°C to afford the desired brazanquinones 1a-1c in reasonable yields (54%–57%) (Scheme 2). The mechanism suggested by us and shown in Scheme 1

• , involves first the preparation of aryllithium intermediates 3 from the carbamates 2a-2b by the reversible metathesis reaction known [21][22][23] as the lithium-halogen exchange which has been widely employed for replacement of a bromine or iodine atom in a substrate by lithium. The intermediate 3 then