- All Non-Carbon B3NO2 Exotic Heterocycles: Synthesis, Dynamics, and Catalysis
-
The B3NO2 six-membered heterocycle (1,3-dioxa-5-aza-2,4,6-triborinane=DATB), comprising three different non-carbon period 2 elements, has been recently demonstrated to be a powerful catalyst for dehydrative condensation of carboxylic acids and amines. The tedious synthesis of DATB, however, has significantly diminished its utility as a catalyst, and thus the inherent chemical properties of the ring system have remained virtually unexplored. Here, a general and facile synthetic strategy that harnesses a pyrimidine-containing scaffold for the reliable installation of boron atoms is disclosed, giving rise to a series of Pym-DATBs from inexpensive materials in a modular fashion. The identification of a soluble Pym-DATB derivative allowed for the investigation of the dynamic nature of the B3NO2 ring system, revealing differential ring-closing and -opening behaviors depending on the medium. Readily accessible Pym-DATBs proved their utility as efficient catalysts for dehydrative amidation with broad substrate scope and functional-group tolerance, offering a general and practical catalytic alternative to reagent-driven amidation.
- Opie, Christopher R.,Noda, Hidetoshi,Shibasaki, Masakatsu,Kumagai, Naoya
-
-
Read Online
- Basic cholane derivatives. XI: Comparison between acid and basic derivatives
-
A series of hydroxycholan-24-amines was synthesized; the carboxyl group of starting unconjugated bile acids was transformed into a basic moiety [-NH2, -NHCH3, -N(CH3)2, or -NHCH2C6H5] at C-24. Solubilities, acidities, partition coefficients, and critical micellar concentrations were measured and compared with those of the corresponding bile acids. Because the steroid nucleus in the amines is the same as that in the bile acids, most of the physical-chemical properties of the two compound classes were similar. The amines were more soluble than the corresponding acids; solubilities depended mainly on the number of steroid hydroxyls and, to a lesser extent, on the side chain. Amines are strong bases in water, whereas unconjugated bile acids can be classified as weak acids. N-Benzylamino derivatives have higher log P (P is partition coefficient) values, as a consequence of the bulky hydrophobic substituent; the log P values were almost the same for the amines and the bile acids and depended on the steroid hydroxyls. Amines can self- aggregate at an acidic pH and form cationic micelles; the critical micellar concentrations of amines were of the same order of magnitude as those of bile acids. The introduction of a basic function in the side chain of the cholane moiety increased the antimicrobial activity toward most gram-positive strains.
- Fini,Fazio,Roda,Bellini,Mencini,Guarneri
-
p. 726 - 729
(2007/10/02)
-
- Antimicrobial activity of cholane compounds. Cholic and deoxycholic acids derivatives (Part 1)
-
A series of compounds of (3 α, 5 β, 7 α, 12 α) 3, 7, 12-trihydroxy and (3 α, 5 β, 12 α) 3, 12-dihydroxy-cholanic acids was synthesized and their in vitro antibacterial activity was determined against a variety of Gram-negative and Gram-positive strains. Some of the compounds show an interesting antimicrobial activity against Gram-positive strains.
- Bellini,Quaglio,Guarneri,Cavazzini
-
p. 185 - 190
(2007/10/02)
-