2524-60-9Relevant academic research and scientific papers
Investigation of the electrophilic reactivity of the biologically active marine sesquiterpenoid onchidal and model compounds
Cadelis, Melissa M.,Copp, Brent R.
, p. 2229 - 2235 (2018)
The structure of the sesquiterpene onchidal (6), a component of the defensive secretion of the shell-less mollusc Onchidella binneyi, contains a masked α,β-unsaturated 1,4-dialdehyde moiety, the presence of which has been proposed to be the cause of the feeding deterrent activity exhibited by the mollusc. We have found onchidal acts as an electrophile, reacting rapidly with the model nucleophile n-pentylamine forming diastereomeric aminated pyrrole adducts. Somewhat surprisingly, no reaction was observed between onchidal and n-pentanethiol. Structurally simplified n-pentyl 11–13 and cyclohexylmethyl 15–17 analogues of onchidal were prepared and demonstrated similar amine-selective reactivity. Onchidal and analogues reacted with the model protein lysozyme, forming covalent adducts and leading to protein cross-linking. These results provide preliminary evidence supporting the molecular mechanism of biological activity exhibited by onchidal.
Stereoselective synthesis of 2-aminocyclobutanols via photocyclization of α-amido alkylaryl ketones: Mechanistic implications for the Norrish/Yang reaction
Griesbeck, Axel G.,Heckroth, Heike
, p. 396 - 403 (2007/10/03)
A series of chiral N-acylated α-amino p-methylbutyrophenone derivatives 1a-1h was synthesized from α-amino acids via a three-step procedure. These substrates were photolyzed in benzene and gave Norrish II and Norrish I cleavage products as well as the N-acylated 2-aminocyclobutanols that derive from γ-hydrogen abstraction and 1,4-triplet biradical combination (Yang cyclization). The products were formed with characteristic Yang/cleavage ratios. The quantum yields for the photodecomposition of the N-acetyl-protected substrates 1b,e,f were moderate (12-26%); the diastereoselectivities of the cyclobutanol formation were remarkably high for all substrates. High diastereospecificity was observed for the isoleucine derivatives (2S,3S)-1g and allo-(2S,3R)-1g; the Yang reaction dominated the photochemistry of allo-1g, whereas 1g gave preferentially Norrish II cleavage. The role of hydrogen bonding as one of the stereo-directing effects was demonstrated by comparison of the cyclization efficiency of the valine derivative 1e with 1h,i,j. Also, aromatic β-keto esters gave the Yang cyclization products in low yields. The diastereoselectivity of the cyclobutanol formation was rationalized by a three-step mechanism where every step is connected with one distinct stereochemical induction mechanism: (a) diastereoselective hydrogen abstraction, (b) conformational equilibration of the 1,4-tetramethylene biradicals (as calculated by semiempiric methods) controlled by hydrogen bonding, and (c) diastereoselective biradical combination (versus cleavage) influenced by spin-orbit coupling controlled intersystem crossing geometries.
