Looping the lupin: A general synthetic strategy for the construction of the lupin alkaloids has been defined and involves sequential formation of the N1C10 and C6C7 bonds, which are common to compounds of this class of natural products. The generality of the approach is exemplified by the syntheses of (+)‐cytisine, (±)‐anagyrine, and (±)‐thermopsine (see scheme).

[reaction: see text] 1,2-Cyclic sulfamidates undergo regiospecific nucleophilic displacement with either methyl thioglycolate or alpha-amino esters, followed by lactamization (thermal, base-mediated, or cyanide-catalyzed), to give thiomorpholin-3-ones and piperazin-2-ones.

The Kowalski ester homologation protocol has been applied to a representative range of α-amino esters to provide β-amino esters with excellent levels of enantio- and diastereocontrol. A key feature of this chemistry is the nature of the N-protecting group that is employed.

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