Synthesis Golf IV: Plaunotol A full FAQ post has been written on meta.chem.SE, explaining the premise of synthesis golf and the 'rules'. Please take a look at this before answering (if you haven't already). 



This fourth round of golf concerns the synthesis of plaunotol, a peptic ulcer treatment: 

InChI=1S/C20H34O2/c1-17(2)8-5-9-18(3)10-6-12-20(16-22)13-7-11-19(4)14-15-21/h8,10,13-14,21-22H,5-7,9,11-12,15-16H2,1-4H3/b18-10+,19-14+,20-13-




In a departure from previous rounds of synthesis-golf, no stereocentres to worry about (hopefully easier for even more people to get involved), though several challenging alkenes for which the geometry must be controlled. 

You may start from anything commercially available in the Sigma Aldrich catalogue, but to make this 'simple' challenge a bit harder, you must make each of the C=C bonds (i.e. no buying in the alkenes that form the product, but you may use an alkene if it is not preserved into the product).
16 steps total

Longest linear sequence of 9 steps

Synthesis of Precursor 1:



The hydroformylation of allylamine, Rhodium catalysis (drew the product wrong, it has one more carbon please ignore it for now, I drew the right structure in the one-pot step)
Diazotization of product, occurs immediately before addition to other precursors in one-pot step later on (produces precursor 1)




Synthesis of Precursors 2 &amp; 3



Hydroformylation of methylacrolein, Rhodium catalysis (produces precursor 2)
Protection of aldehyde via hemithioacetal
Protection of ketone through dioxolane
Deprotection of aldehyde by base (produces precursor 3)







Formation of grignard reagent by reaction with magensium of bromoethanal diethyl acetal







One pot reaction, diazo thermolysis resulting in carbene substitution followed by aldol
Weak acid dehydration to form alpha-beta unsaturated ketone
Wittig reaction to establish alkene
Dehydration using Rhenium Catalyst with good selectivity, click here for the paper
Reduction of aldehyde (special reducing agent used just in case free ketone exists)





Deprotection of the ketone (loss of ethane-1,2-diol)
Grignard reaction followed by dehydration to form the ketone of the product
Reduction with lithium aluminum hydride (not shown) to get product, Plaunotol