Glucose-sensitive insulin with attenuation of hypoglycaemia.

The risk of inducing hypoglycaemia (low blood glucose) constitutes the main challenge associated with insulin therapy for diabetes. Insulin doses must be adjusted to ensure that blood glucose values are within the normal range, but matching insulin doses to fluctuating glucose levels is difficult because even a slightly higher insulin dose than needed can lead to a hypoglycaemic incidence, which can be anything from uncomfortable to life-threatening. It has therefore been a long-standing goal to engineer a glucose-sensitive insulin that can auto-adjust its bioactivity in a reversible manner according to ambient glucose levels to ultimately achieve better glycaemic control while lowering the risk of hypoglycaemia.

'Reverse biomimetic' synthesis of l-arogenate and its stabilized analogues from l-tyrosine.

l-Arogenate (also known as l-pretyrosine) is a primary metabolite on a branch of the shikimate biosynthetic pathway to aromatic amino acids. It plays a key role in the synthesis of plant secondary metabolites including alkaloids and the phenylpropanoids that are the key to carbon fixation. Yet understanding the control of arogenate metabolism has been hampered by its extreme instability and the lack of a versatile synthetic route to arogenate and its analogues.

Scalable synthesis and coupling of quaternary α-arylated amino acids: α-aryl substituents are tolerated in α-helical peptides.

Quaternary amino acids are important tools for the modification and stabilisation of peptide secondary structures. Here we describe a practical and scalable synthesis applicable to quaternary alpha-arylated amino acids (Q4As), and the development of solid-phase synthesis conditions for their incorporation into peptides. Monomeric and dimeric α-helical peptides are synthesised with varying degrees of Q4A substitution and their structures examined using biophysical methods.

Amino Acid-Derived trans- N-Chloroformylimidazolidinones: Scalable, Stereoselective Synthesis, Structure, and Utility.

N-acyl imidazolidinones, which are key intermediates in the stereoselective synthesis of amino acids by "self-regeneration of stereochemistry" methods, are classically made by only moderately diastereoselective methods. We now report that cyclization of pivaldimino-amides with phosgene in the presence of pyridine may be made fully diastereoselective for the trans-N-chloroformylimidazolidinones, and we detail the conformational features of the products. We show that despite the presence of the electrophilic carbamoyl chloride function the products show remarkable stability and may be deprotonated to form enolates with useful reactivity for the synthesis of amino acid derivatives.

Substituted Dihydroisoquinolinones by Iodide-Promoted Cyclocarbonylation of Aromatic α-Amino Acids.

Imidazolidinone derivatives of a range of aromatic α-amino acids, on treatment with phosgene and potassium iodide, undergo a mild Bischler-Napieralski-style cyclocarbonylation reaction that generates a tricyclic lactam by insertion of a C═O group between amino acid nitrogen and the ortho position of the aryl substituent. Regio- and diastereoselective functionalization of the lactam generates a library of substituted dihydroisoquinolinones and their congeners in enantioenriched form.

Asymmetric α-arylation of amino acids.

Quaternary amino acids, in which the α-carbon that bears the amino and carboxyl groups also carries two carbon substituents, have an important role as modifiers of peptide conformation and bioactivity and as precursors of medicinally important compounds. In contrast to enantioselective alkylation at this α-carbon, for which there are several methods, general enantioselective introduction of an aryl substituent at the α-carbon is synthetically challenging. Nonetheless, the resultant α-aryl amino acids and their derivatives are valuable precursors to bioactive molecules.

Intramolecular arylation of amino acid enolates.

Dianionic enolates formed from N'-aryl urea derivatives of amino acids undergo intramolecular C-arylation by attack of the enolate anion on the N'-aryl ring, leading to a hydantoin derivative of a quaternary amino acid. In situ IR studies allow identification of four intermediates on the reaction pathway.