Total Synthesis of +-alexine by utilizing a highly stereoselective [3+2] annulation reaction of an N-tosyl-alpha-amino aldehyde and a 1,3-bis(silyl)propene.
A novel route towards the polyhydroxylated pyrrolizidine alkaloid (+)-alexine has been developed. A key step in this synthesis is a highly stereoselective [3+2] annulation reaction of N-Ts-alpha-amino aldehyde 7 a (Ts=tosyl) and 1,3-bis(silyl)propene 8 a for the construction of the polyhydroxylated pyrrolidine subunit of the target molecule. Previous synthetic strategies rely on carbohydrates that require several protecting-group manipulations, thereby making the total number of steps relatively high. The [3+2] annulation strategy compares favorably with carbohydrate-based syntheses and constitutes a highly efficient entry to polyhydroxylated alkaloids.
Dressel
Martina
M
Organic Chemistry, KTH Chemical Science and Engineering, Royal Institute of Technology, Teknikringen 36, 10044 Stockholm, Sweden.
Restorp
Per
P
Somfai
Peter
P
D000447:Aldehydes / Q000737:chemistry*; D003500:Cyclization; D015394:Molecular Structure; D017646:Organosilicon Compounds / Q000737:chemistry*; D011763:Pyrrolizidine Alkaloids / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism
D000447:Aldehydes; D017646:Organosilicon Compounds; D011763:Pyrrolizidine Alkaloids; C059794:australine