Synthesis of d-biotin from L-cystine via intramolecular [3+2]cycloaddition

Abstract

11) Interestingly, modest threo selectivity has also been observed in the Lewis acid catalyzed aldol condensations of (¿)-0-silyl ketene acetals derived from ethyl propionate:

Zinc-Acetic Acid Reductive Cyclisation in a Two-Step Synthesis of the S1-N10 Nine-Membered Lactone Core ofent-Griseoviridin

“…Nevertheless, carrying out the reaction in the presence of zinc in acetic acid 8 resulted in an improved yield of lactone 13 (51%). This result was quite noteworthy, considering that no favourable Thorpe-Ingold effect favours this '9-endo-dig' cyclisation into an unsaturated nine-membered lactone.…”

Biotin: A Timeless Challenge for Total Synthesis

“…Baggiolini and co-workers at Hoffmann-La Roche have reported two syntheses (1982 and 1987) in which the same bond formation between C-2 and C-3 was realized via an intramolecular [3 + 2] dipolar cycloaddition. , The first of these provides a nice example of the use of a cyclic template to enforce the stereochemical outcome of a reaction into the desired sense (Scheme ) …”

Readily Available Chiral Carbon Fragments and Their Use in Synthesis

“…In addition to carbohydrate based approaches to biotin, in which inorganic sulfide is incorporated, preparations of this vitamin from the sulfurcontaining amino acids cysteine and cystine have been reported (509,510). In the first such sequence (509) (Scheme 96), the Hoffmann-La Roche group converted the protected cysteine 1237, by reduction and oxidation, to aldehyde 1238.…”