Racemic bicyclopropylidenyl‐ (rac‐11) and methylenespiropentyl‐ (rac‐17) substituted alanines have been synthesized by iodination of bicyclopropylidenyl‐ and methylenespiropentylmethanols 7, 13, nucleophilic substitution of the iodine in 8, 14 with the enolate of ethyl α‐(diphenylmethyleneamino)acetate (O'Donnell's glycine equivalent) and deprotection of 9, 15 in 24 and 18% overall yield, respectively. N‐Methylbicyclopropylidenylalanine rac‐22, was obtained from the Michael adduct of (bicyclopropylidenyl)magnesium bromide 18 to enamine 19 and deprotection of the carbamate 20 (23% overall yield). Racemic (1‐amino‐2‐methylenespiropentane)‐ (37), (1‐amino‐2‐methylenecyclopropane)‐ (3), and (1‐aminobicyclopropylidene)carboxylic acid (39) were prepared as hydrochlorides by tert‐butoxycarbonylation of the lithiated methylenespiropentane (6), methylenecyclopropane (4), or bicyclopropylidene (5) intermediates with di‐tert‐butyl pyrocarbonate (Boc2O), repeated lithiation of the tert‐butyl esters 29, 30, and 33 with LDA and subsequent carboxylation, Curtius degradation of the half esters 31, 32, and 34 followed by deprotection in 11, 45, and 4% overall yields, respectively. Compound 37 was also prepared from bicyclopropylidene (5) following the same procedure, but with rearrangement in the last but one step, in 19% overall yield. An attempted Hofmann degradation of the bicyclopropylidenecarboxamido ester 40 with NBS failed and gave only bromohydrin 44 (27%), but with bis(acetoxy)iodobenzene provided carbamate 46a, b in 76 amd 79% yield, respectively. Along this route with subsequent deprotection of 46b, the amino acid 39 could be prepared in up to 10% overall yield from bicyclopropylidene.
