Details associated with the bimolecular 1,4-dipolar cycloaddition reaction of cross-conjugated heteroaromatic betaines

Recent developments in syntheses of the post-secodine indole alkaloids. Part III: Rearranged alkaloid types

The third part of a planned review on developments in the field of total and formal total synthesis of the post-secodine indole alkaloids focuses on types of rearranged alkaloids, i.e. on the skeletons with altered connectivities next to the indol(e)ine moiety, especially with a new bond to N-1. It reviews the synthesis of melodane, goniomitine, chippiine/dippinine, lirofoline and tronocarpine alkaloids, as well as alkaloids of secoschizozygane/vallesamidine, schizozygane and isoschizozygane type. It covers the literature from approximately 1991 up to May 2011. A review with 115 references.

Translation of Pseudo-Cross-Conjugation into Chemistry: Cycloadditions of Mesomeric Betaines to the New Ring System Spiro[indazole-3,3‘-pyrrole]

Indazolium-3-amidates (X-ray analysis), readily available on trapping the N-heterocyclic carbene indazol-3-ylidene with isocyanates, underwent [3+2]-cycloadditions with activated triple bonds to spiro[indazole-3,3'-pyrroles]. A combination of NMR techniques such as heteronuclear single quantum coherence (HSQC), heteronuclear multiple bond correlation (HMBC), nuclear Overhauser enhancement spectroscopy (NOESY), and 1H/15N correlations were applied to elucidate the structures of the cycloadducts.

An Approach to the Isoschizozygane Alkaloid Core Using a 1,4-Dipolar Cycloaddition of a Cross-Conjugated Heteroaromatic Betaine

[reaction: see text] A new strategy for the synthesis of the isoschizozygane alkaloid core has been developed that is based on a 1,4-dipolar cycloaddition reaction of a cross-conjugated heteroaromatic betaine. The resulting cycloadduct undergoes loss of COS, and further reduction delivers a 5a-aza-acenaphthylene intermediate that was transformed into the isoschizozygane skeleton upon treatment with acid.

Biphenylsulfonamide endothelin receptor antagonists. 4. Discovery of N-[[2'-[[(4,5-dimethyl-3-isoxazolyl)amino]sulfonyl]-4-(2-oxazolyl)[1,1'-biphenyl]- 2-yl]methyl]-N,3,3-trimethylbutanamide (BMS-207940), a highly potent and orally active ET(A) selective antagonist

We have previously disclosed the selective ET(A) receptor antagonist N-(3,4-dimethyl-5-isoxazolyl)-4'-(2-oxazolyl)[1,1'-biphenyl]-2-sulfonamide (1, BMS-193884) as a clinical development candidate. Additional SAR studies at the 2'-position of 1 led to the identification of several analogues with improved binding affinity as well as selectivity for the ET(A) receptor. Following the discovery that a 3-amino-isoxazole group displays significantly improved metabolic stability in comparison to its 5-regioisomer, the 3-amino-isoxazole group was combined with the optimal 2'-substituent leading to 16a (BMS-207940). Compound 16a is an extremely potent (ET(A) K(i) = 10 pM) and selective (80,000-fold for ET(A) vs ET(B)) antagonist. It is also 150-fold more potent and >6-fold more selective than 1. The bioavailability of 16a was 100% in rats and the systemic clearance and volume of distribution are higher than that of 1. In rats, intravenous 16a blocks big ET pressor responses with 30-fold greater potency than 1. After oral dosing at 3 micromol/kg, 16a displays enhanced duration relative to 1.