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