Bistratamide

In their synthesis of the macrocyclic hexapeptide bistratamide D, Meyers and co-workers prepared the tran -oxazoline 70 from the corresponding cw-oxazo-line 69 through several steps, the last of which was cyclization to the oxazoline using Burgess reagent. The net outcome is inversion of the stereocenter at the 5-position of the oxazoline (Scheme 8.25). 

Cyclohexapept bistratamides Lissoclinum spp., Didemnidae, Ascid. from GBR and the Philippines Foster, 1992) comoramides Didemnum molle, Didemnidae from Comoro Is Rudi 1998) Oiexalpatellins Lissoclinum sp. from Fiji Is. Carroll 1996). 

Foster, M.P. Conception, G.P. Caraan, G.B. Ireland, C.M. (1992) Bistratamides C and D. Two new oxazole-containing cyclic hexapeptides isolated from a Philippine Lissoclinum bistratum ascidian. J. Org. Chem., 57, 6671-5. 

Lissoclinum species of tunicates produce a range of cyclic peptides, which contain thiazole, thiazoline and oxazoline rings. Most belong to the general families patellamides (octapeptides), lissoclinamides (heptapeptides) or bistratamides (hexapeptides) [22],... 

Table 6. Thiazole/Thiazoline Bistratamide Hexapeptides Isolated from the Tunicate Lissoclinium bistratum...

During this time, the total synthesis of several marine sulfur-containing natural products cited in this review has been reported and they confirmed the suggested structures. This is the case of the synthesis of some sulfonoceramides (e.g. flavocristamide A (318) discussed in the sulfonic acid and their derivatives section [366], and the synthesis of the thiazole-containing compounds bistratamide D (381) [367], trunkamide (388) [368], mollamide (393) [369], dolastatin I (409) [370], and virenamide B (414) [371]. 

A Ph3P0/Tf20-mediated cyclodehydration was utilized in the conversion of -keto-ester 249 to give a key oxazole building block 250 (Scheme 121), which was used in a total synthesis of the marine natural product bistratamide F-I <2005T241, CHEC-III(4.04.9.1)517>. 

A library of cyclic peptides was obtained by the cyclooligomerization of mixtures of azole-based amino acids. This synthetic approach was applied to the synthesis of bistratamide H and didmolamide A, cyclic peptides containing oxazole rings <07OBC1541>. Other cyclic scaffolds based on oxazole peptides were published <07EJO1779 07T9862 07NAR3272>. 

Bistratamides C-J, 381-388, are a group of hexapeptides isolated from the ascidian Lissoclinum bistratum collected from Tablas Island in the Philippines <2003JNP247, 2004CEJ71>. 

Compounds isolated from ascidians Ascidiacyclamide Bistratamide A,B Bistratamide C Bistratamide D,F,G,I Bistratamide E,H,J Comoramide A,B Cyclodidemnamide... 

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