2-Allylphenyl glycosides as complementary building blocks for oligosaccharide and glycoconjugate synthesis

• Hemali D. Premathilake and
• Alexei V. Demchenko

Beilstein J. Org. Chem. 2012, 8, 597–605, doi:10.3762/bjoc.8.66

• efficient oligosaccharide assembly. Keywords: carbohydrates; glycosylation; leaving group; oligosaccharides; orthogonal strategy; selective activation; Introduction Current knowledge about the key roles of carbohydrates is still limited. However, thanks to the explosive growth of the field of glycobiology

• oligosaccharide assembly by minimizing or even eliminating additional manipulations between coupling steps, are based either on chemoselective or on selective activation of leaving groups [6]. The use of selective activation [7] offers more flexibility than that of the chemoselective activation which relies on

• the nature of the protecting groups [8], and Ogawa’s orthogonal strategy is conceptually the most attractive approach that has been developed to date [9][10][11][12]. This technique implies the use of two orthogonal leaving groups, LGa and LGb, the selective activation of which can be reiterated to

Triazole–Au(I) complex as chemoselective catalyst in promoting propargyl ester rearrangements

• Dawei Wang,
• Yanwei Zhang,
• Rong Cai and
• Xiaodong Shi

Beilstein J. Org. Chem. 2011, 7, 1014–1020, doi:10.3762/bjoc.7.115

• process [35]. As shown in Scheme 2b, with the [IPr–Au]+ catalyst, only trace amount of the allene 2a was obtained. The major product derived from the Friedel–Crafts addition of the aromatic ring to the gold activated allene. Therefore, selective activation of the alkyne over the allene was considered as a

Gold-catalyzed heterocyclizations in alkynyl- and allenyl-β-lactams

• Benito Alcaide and
• Pedro Almendros

Beilstein J. Org. Chem. 2011, 7, 622–630, doi:10.3762/bjoc.7.73

• (DFT) calculations were performed to obtain insight on various aspects of this reactivity and indicated the selective activation of the allene and alkyne component. Free energy profile [kcal mol–1] for the transformation of γ-allenol I into the tetrahydrofuran type 9. Gold-catalyzed cyclization of 4

Diels- Alder reactions using 4,7-dioxygenated indanones as dienophiles for regioselective construction of oxygenated 2,3-dihydrobenz[f]indenone skeleton

• Natsuno Etomi,
• Takuya Kumamoto,
• Waka Nakanishi and
• Tsutomu Ishikawa

Beilstein J. Org. Chem. 2008, 4, No. 15, doi:10.3762/bjoc.4.15

• -Trioxygenated 2,3-dihydrobenz[f]indenone derivative 21 was exclusively formed on DAR of indanetrione 8 and diene 7 because of selective activation of the C6 carbon due to the presence of additional cross conjugation between the C1 and the C4 carbonyl groups (TS-A, Figure 4). Semiempirical calculation [44] of

Synthesis of 2,6-trans- disubstituted 5,6-dihydropyrans from (Z)-1,5-syn-endiols

• Eric M. Flamme and
• William R. Roush

Beilstein J. Org. Chem. 2005, 1, No. 7, doi:10.1186/1860-5397-1-7

• hydroxyl groups. Selective activation of the allylic alcohol in 2 as a leaving group followed by nucleophilic attack by the homoallylic alcohol will lead to dihydropyran 3. However, activation of the homoallylic alcohol followed by nucleophilic attack by the allylic alcohol will provide the enantiomeric