Combining the best of both worlds: radical-based divergent total synthesis

• Kyriaki Gennaiou,
• Antonios Kelesidis,
• Maria Kourgiantaki and
• Alexandros L. Zografos

Beilstein J. Org. Chem. 2023, 19, 1–26, doi:10.3762/bjoc.19.1

• and the aromatic moieties present in these natural products and provided the common synthetic intermediate 70 (Scheme 6). The diverse tetracycles were accessed either via an intramolecular radical cyclization of the reduced congener 73 or through a Heck reaction of intermediate 71. Reaction of 73 with

Dipolar addition to cyclic vinyl sulfones leading to dual conformation tricycles

• Steven S. Y. Wong,
• Michael G. Brant,
• Christopher Barr,
• Allen G. Oliver and
• Jeremy E. Wulff

Beilstein J. Org. Chem. 2013, 9, 1419–1425, doi:10.3762/bjoc.9.159

• the origin of the fluxional behavior was probed by NMR methods together with DFT calculations. This behavior was ultimately attributed to stereochemical inversion at one of two nitrogen centers embedded in the tricyclic framework. Two tetracycles were also synthesized, and the degree of signal

• the preparation of the analogous tetracycles, through the use of bicyclic vinyl sulfones as substrates. To this end, we attempted to react dipoles 2a and 2b with the readily prepared [39] bicycle 1b (Table 3, entry 1). Unfortunately, no cycloaddition adducts were observed even when additional heating

Dipyrazolo[1,5-a:4',3'-c]pyridines – a new heterocyclic system accessed via multicomponent reaction

• Wolfgang Holzer,
• Gytė Vilkauskaitė,
• Eglė Arbačiauskienė and
• Algirdas Šačkus

Beilstein J. Org. Chem. 2012, 8, 2223–2229, doi:10.3762/bjoc.8.251

• resulted in the formation of tetracycles 5j–l in acceptable yields (Table 1, entries 10–12). NMR spectroscopic investigations The NMR spectroscopic data of all compounds described in this study are given in Supporting Information File 1. Unequivocal assignment of resonances was carried out by the combined

Asymmetric Brønsted acid-catalyzed aza-Diels–Alder reaction of cyclic C-acylimines with cyclopentadiene

• Magnus Rueping and
• Sadiya Raja

Beilstein J. Org. Chem. 2012, 8, 1819–1824, doi:10.3762/bjoc.8.208

• optically active aza-tetracycles in good yields with high diastereo- and enantioselectivities under mild reaction conditions. Keywords: BINOL phosphate; [4 + 2] cycloaddition; Diels–Alder reaction; organocatalysis; Introduction The enantioselective aza-Diels–Alder reaction is an important method for the

• products with low enantioselectivities [52][53][54][55]. Conclusion In conclusion, we have developed an enantioselective Brønsted acid catalyzed aza-Diels–Alder reaction of C-acylimines with cyclopentadiene. The corresponding aza-tetracycles were obtained in high yields and with excellent enantio- and

Novel tetracyclic structures from the synthesis of thiolactone-isatin hybrids

• Renate Hazel Hans,
• Hong Su and
• Kelly Chibale

Beilstein J. Org. Chem. 2010, 6, No. 78, doi:10.3762/bjoc.6.78

• ; hybrids; isatin; tetracycles; thiolactomycin; thiolactone; Introduction Hybrid structures have been found in nature and their synthesis has become a useful drug discovery strategy for new anti-infective agents [1]. Improved pharmacokinetics, therapeutic and toxicity profiles have been reported for

• the formation of by-products (tetracycles) observed in the reaction of 5 with the N-alkylated isatin intermediates 6 bearing the n = 3–5 linkers (Table 1). The tetracycle 4 had a slightly lower Rf than the desired hybrid 3 and was colorless or light yellow compared to the orange-colored hybrid 3. We

• in the tetracycles 4 was further sparked by the ease and simplicity of their preparation, and the novelty of their architecture as revealed by single X-ray crystal structure analysis. Attractive structural features of 4 include two vicinal quaternary stereocenters and a complex, bicyclic ring system