Selected Synthetic Strategies to Spirocyclics

Abstract

The design and synthesis of spirocycles is a challenging task because it involves the creation of a quaternary center, which itself is considered to be one of the most difficult tasks among synthetic transformations. Some recent approaches based on metathesis, cycloaddition and transition-metal-mediated transformations to spirocycles are described here.

Bis(spirolactam) 1,3-double-armed calix[4]arene compounds and their application as extractants for the determination of heavy metal ions

“…The most selective of this group of hosts was compound 14, with the pendant N-benzyl groups. Like their -OH analogues, the -OMe compounds (12)(13)(14) showed negligible extraction efficiency (<30%) towards the alkaline and alkali metal ions (data not shown).…”

“…Spirolactam derivatised calixarene 13 was prepared in a similar manner to that described for 12 using trifluoroacetate salt 2 [17]. A solid residue was purified was purified by column chromatography on silica gel with 5% methanol/dichloromethane to give 13 as an off white solid (0.17 g, 54% [4]arene (14). Spirolactam derivatised calixarene 14 was prepared in a similar manner to that described for 12 using trifluoroacetate salt 3 [17].…”

“…Another way to constrain the flexibility of small molecules is by incorporating a spirocyclic fusion into the molecule [13,14]. This gives a defined conformation with directionality to any ligating groups within the spirocyclic moiety.…”

Anomeric spirocycles by solvent incorporation: reactions of O-peracylated (glyculopyranose and glyculopyranosyl bromide)onamide derivatives with ketones

“…Synthetic strategies to obtain spirocycles were amply 50 reviewed, [1][2][3] and ring closure of geminally disubstituted cyclic compounds were highlighted as one of several generally applied approaches towards various spiro derivatives. Following this principle for the preparation of anomeric spirocycles the necessary starting compounds can be selected from monosaccharides homo-or heterobifunctionalized at the anomeric centre.…”

“…[1][2][3] Spirocycles involving the anomeric carbon of monosaccharide derivatives are also well known, and have been, among others, shown to possess antiparasitic, 4 antibacterial, antifungal, 5 antidiabetic, 6 herbicide, 7 glycosidase [8][9][10] and glycogen phosphorylase 11 inhibitory activities.…”