Amygdalin (d-Mandelonitrile 6-O-β-d-glucosido-β-d-glucoside) is a natural cyanogenic glycoside occurring in the seeds of some edible plants, such as bitter almonds and peaches. It is a medically interesting but controversial compound as it has anticancer activity on one hand and can be toxic via enzymatic degradation and production of hydrogen cyanide on the other hand. Despite numerous contributions on cancer cell lines, the clinical evidence for the anticancer activity of amygdalin is not fully confirmed. Moreover, high dose exposures to amygdalin can produce cyanide toxicity. The aim of this review is to present the current state of knowledge on the sources, toxicity and anticancer properties of amygdalin, and analytical methods for its determination in plant seeds.

This comprehensive review, covering the years 1968–2022, is not only a retrospective investigation of a certain group of linearly fused aromatics, called acenes, but also a presentation of the current state of the knowledge on the synthesis, reactions, and applications of these compounds. Their characteristic feature is substitution of the aromatic system by one, two, or three organophosphorus groups, which determine their properties and applications. The (P^III, P^IV, P^V) phosphorus atom in organophosphorus groups is linked to the acene directly by a P-C_sp2 bond or indirectly through an oxygen atom by a P-O-C_sp2 bond.

Two heteroatom-variants of the Friedel-Crafts/Bradsher cyclization of o-acetalaryl(aryl)methyl ethers and o-dithioacetalaryl(aryl)methyl thioethers, have been realized with the ultrasound assistance. The environmentally friendly "oxo-variant" (Oxo-F-C/B), proceeding in a medium containing mineral acid and a large amount of water (HClaq/CH3CN) led to a very efficient formation of RO-substituted (hetero)acenes in less than 5 min. In the "thio-variant" (Thio-F-C/B), o-dithioacetalaryl(aryl)methyl thioethers underwent ultrasound-assisted cyclization in nonaqueous medium (FeCl3/KI/EtOH) in less than 25 min., in lower yields than in the "oxygen variant" to give RS-substituted (hetero)acenes. The RO-(hetero)acenes cyclized at 25-60 °C in aqueous media but did not cyclize in organic solvents while the RS-(hetero)acenes required higher temperatures 55-60 °C and cyclized in organic solvents but did not react in aqueous media. The acceleration of the ultrasound-assisted reactions compared to the reactions carried out under silent conditions exceeded 7500 times in the most effective example of the oxo-variant and on average 2 times for the thio-variant. The plausible reaction mechanisms under ultrasound and silent conditions have been proposed. The ultrasonic mechanism involves disturbing of solvation layers and formation of the reactive ("naked") carbocations upon operation of the shock wave produced by the bubble collapse. The o-acetalaryl(aryl)methyl ethers underwent a selective ultrasound-assisted deacetalization to give o-formylaryl(aryl)methyl ethers, without subsequent cyclization under the acidic reaction conditions.

While few studies show only symmetrical and poorly mono-SO_n (n = 0–2) substituted acenes, in this study, we present a synthesis of a new group of unsymmetrical, significantly substituted derivatives, which revealed unique photophysical properties. Both sulfides (S), sulfoxides (SO) and sulfones (SO₂) showed very high photochemical stabilities, unusual for these groups, during UV-irradiation at 254/365 nm (air O₂ and Ar), which was higher than any found in the literature. For the (S)/(SO) series (254 nm), the stabilities of 80–519 min. (air O₂ and Ar) were found. At 365 nm, stabilities of 124—812 min./(air O₂) for (S)/(SO) and higher for (SO₂) were observed. Photoluminescence lifetimes of (SO_n) of the lower anthryl symmetry remained in the following order: (SO₂) < (S) < (SO); those with full symmetry were in the following order: (S) < (SO) < (SO₂). The enhanced photostability was explained with DFT/MS/Hammett’s constants, which showed the leading role of the SO_n groups in stabilization of HOMO/LUMO frontier orbitals. The SO_n (n = 0–2) substituted acenes turned out to be tunable violet/blue/green emitters by oxidation of S atoms and the introduction of rich substitution.

New thiophosphates containing functionalized cyclic ketone derivatives as ligands have been stereoselectively prepared from readily available starting materials. Full axial stereoselectivity of the NaBH4 reduction of the carbonyl group in thiophosphates providing the corresponding thiols or sulfides has been demonstrated. The sulfides have been transformed into new functionalized cyclic Baylis–Hillman type adducts of defined configuration. The prospects for the useful synthetic application of these adducts appear to be very promising.