Racemic bicyclopropylidenyl-(rac-11) and methylenespiro-cyclopropylidene (5) intermediates with di-tert-butyl pyrocarbonate (Boc 2 O), repeated lithiation of the tert-butyl esters pentyl-(rac-17) substituted alanines have been synthesized by iodination of bicyclopropylidenyl-and methylenespiro-29, 30, and 33 with LDA and subsequent carboxylation, Curtius degradation of the half esters 31, 32, and 34 followed by pentylmethanols 7, 13, nucleophilic substitution of the iodine in 8, 14 with the enolate of ethyl α-(diphenylmethyleneamideprotection in 11, 45, and 4% overall yields, respectively.
Compound 37 was also prepared from bicyclopropylidene (5) no)acetate (O'Donnell's glycine equivalent) and deprotection of 9, 15 in 24 and 18% overall yield, respectively. N-Methyl-following the same procedure, but with rearrangement in the last but one step, in 19% overall yield. An attempted Hof-bicyclopropylidenylalanine rac-22, was obtained from the Michael adduct of (bicyclopropylidenyl)magnesium bromide mann degradation of the bicyclopropylidenecarboxamido ester 40 with NBS failed and gave only bromohydrin 44 18 to enamine 19 and deprotection of the carbamate 20 (23% overall yield). Racemic (1-amino-2-methylenespiropentane)-(27%), but with bis(acetoxy)iodobenzene provided carbamate 46a,b in 76 amd 79% yield, respectively. Along this (37), (1-amino-2-methylenecyclopropane)-(3), and (1-aminobicyclopropylidene)carboxylic acid (39) were prepared as hy-route with subsequent deprotection of 46b, the amino acid 39 could be prepared in up to 10% overall yield from bicyclo-drochlorides by tert-butoxycarbonylation of the lithiated methylenespiropentane (6), methylenecyclopropane (4), or bi-propylidene.