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The reaction of cyclic ethers with iodoxyl radical iodine oxide [generated by irradiation of iodine oxide formed in situ with red mercury(II) oxide and iodine] gives the corresponding ω-iodoalkyl formates in one step; tetrahydrofuran can be transformed into ω-iodoalkyl formate in 31% yield. Aldehyde cyclic acetals under conditions similar to the reaction of cyclic ethers lead to monoesters of α,ω-alkanediols in one step; cyclohexanecarboxaldehyde ethylene acetal gives 2-hydroxy cyclohexanecarboxylate in 60% yield. The pathways leading to ω-iodoalkyl formates and monoesters of α,ω-alkanediols are discussed based on the results of 18O-labelling studies with 18·OI and I218O.

L-Aspartic acid by regioselective modification of the α-carboxylic acid group, namely N-tosylation, anhydride formation, reduction, iodo-esterification, alkylation, and deprotection afforded a series of γ-alkyl β-aminobutyric acids of the R configuration (ee>99%).

L‐Aspartic acid by tosylation, anhydride formation, and reduction with NaBH₄ was converted into (3S)‐3‐(tosylamino)butan‐4‐olide (8; Scheme 1). Tretment of 8 with ethanolic trimethylsilyl iodide gave the N‐protected deoxy‐iodo‐β‐homoserine ethyl ester 9. The latter, on successive nucleophilic displacement with lithium dialkyl‐cuprates ( → 10a–e), alkaline hydrolysis ( → 11a–e), and reductive removal of the tosyl group, produced the corresponding 4‐substituted (3R)‐3‐aminobutanoic acids 12a–e (ee > 99%). Electrophilic hydroxylation of 8 ( → 19; Scheme 3), subsequent iodo‐esterification ( → 21; Scheme 4), and nucleophilic alkylation and phenylation afforded, after saponification and deprotection, a series of 4‐substituted (2S, 3R)‐3‐amino‐2‐hydroxybutanoic acids 24 including the N‐terminal acids 24e ( =3) and 24f ( =4) of bestatin and microginin (de > 95%), respectively.